diff --git a/htdocs/core/lib/functions.lib.php b/htdocs/core/lib/functions.lib.php
index f592b20ceea..c306005cffe 100644
--- a/htdocs/core/lib/functions.lib.php
+++ b/htdocs/core/lib/functions.lib.php
@@ -9765,10 +9765,10 @@ function dol_getmypid()
  *                                      like "keyword1 keyword2" = We want record field like keyword1 AND field like keyword2
  *                                      or like "keyword1|keyword2" = We want record field like keyword1 OR field like keyword2
  *                             			If param $mode is 1, can contains an operator <, > or = like "<10" or ">=100.5 < -1000"
- *                             			If param $mode is 2, can contains a list of int id separated by comma like "1,3,4"
- *                             			If param $mode is 3, can contains a list of string separated by comma like "a,b,c"
- * @param	integer			$mode		0=value is list of keyword strings, 1=value is a numeric test (Example ">5.5 <10"), 2=value is a list of ID separated with comma (Example '1,3,4')
- * 										3=value is list of string separated with comma (Example 'text 1,text 2'), 4=value is a list of ID separated with comma (Example '2,7') to be used to search into a multiselect string '1,2,3,4'
+ *                             			If param $mode is 2 or -2, can contains a list of int id separated by comma like "1,3,4"
+ *                             			If param $mode is 3 or -3, can contains a list of string separated by comma like "a,b,c".
+ * @param	integer			$mode		0=value is list of keyword strings, 1=value is a numeric test (Example ">5.5 <10"), 2=value is a list of ID separated with comma (Example '1,3,4'), -2 is for exclude list,
+ * 										3=value is list of string separated with comma (Example 'text 1,text 2'), -3 if for exclude list, 4=value is a list of ID separated with comma (Example '2,7') to be used to search into a multiselect string '1,2,3,4'
  * @param	integer			$nofirstand	1=Do not output the first 'AND'
  * @return 	string 			$res 		The statement to append to the SQL query
  * @see dolSqlDateFilter()
@@ -9783,7 +9783,7 @@ function natural_search($fields, $value, $mode = 0, $nofirstand = 0)
 		$value = preg_replace('/\*/', '%', $value); // Replace * with %
 	}
 	if ($mode == 1) {
-		$value = preg_replace('/([!<>=]+)\s+([0-9'.preg_quote($langs->trans("DecimalSeparator"), '/').'\-])/', '\1\2', $value); // Clean string '< 10' into '<10' so we can the explode on space to get all tests to do
+		$value = preg_replace('/([!<>=]+)\s+([0-9'.preg_quote($langs->trans("DecimalSeparator"), '/').'\-])/', '\1\2', $value); // Clean string '< 10' into '<10' so we can then explode on space to get all tests to do
 	}
 
 	$value = preg_replace('/\s*\|\s*/', '|', $value);
@@ -9794,16 +9794,15 @@ function natural_search($fields, $value, $mode = 0, $nofirstand = 0)
 		$fields = array($fields);
 	}
 
-	$j = 0;
-	foreach ($crits as $crit) {
+	$i1 = 0;	// count the nb of and criteria added (all fields / criterias)
+	foreach ($crits as $crit) {		// Loop on each AND criteria
 		$crit = trim($crit);
-		$i = 0;
-		$i2 = 0;
+		$i2 = 0;	// count the nb of valid criteria added for this this first criteria
 		$newres = '';
 		foreach ($fields as $field) {
 			if ($mode == 1) {
 				$tmpcrits = explode('|', $crit);
-				$i3 = 0;	// count the nb of valid criteria added for this field
+				$i3 = 0;	// count the nb of valid criteria added for this current field
 				foreach ($tmpcrits as $tmpcrit) {
 					if ($tmpcrit !== '0' && empty($tmpcrit)) {
 						continue;
@@ -9830,7 +9829,7 @@ function natural_search($fields, $value, $mode = 0, $nofirstand = 0)
 						$i3++; // a criteria was added to string
 					}
 				}
-				$i2++;
+				$i2++; // a criteria for 1 more field was added to string
 			} elseif ($mode == 2 || $mode == -2) {
 				$crit = preg_replace('/[^0-9,]/', '', $crit); // ID are always integer
 				$newres .= ($i2 > 0 ? ' OR ' : '').$field." ".($mode == -2 ? 'NOT ' : '');
@@ -9838,7 +9837,7 @@ function natural_search($fields, $value, $mode = 0, $nofirstand = 0)
 				if ($mode == -2) {
 					$newres .= ' OR '.$field.' IS NULL';
 				}
-				$i2++; // a criteria was added to string
+				$i2++; // a criteria for 1 more field was added to string
 			} elseif ($mode == 3 || $mode == -3) {
 				$tmparray = explode(',', $crit);
 				if (count($tmparray)) {
@@ -9851,7 +9850,7 @@ function natural_search($fields, $value, $mode = 0, $nofirstand = 0)
 						}
 					}
 					$newres .= ($i2 > 0 ? ' OR ' : '').$field." ".($mode == -3 ? 'NOT ' : '')."IN (".$db->sanitize($listofcodes, 1).")";
-					$i2++; // a criteria was added to string
+					$i2++; // a criteria for 1 more field was added to string
 				}
 				if ($mode == -3) {
 					$newres .= ' OR '.$field.' IS NULL';
@@ -9868,20 +9867,20 @@ function natural_search($fields, $value, $mode = 0, $nofirstand = 0)
 							$newres .= ' OR '.$field." LIKE '%,".$db->escape($val)."'";
 							$newres .= ' OR '.$field." LIKE '%,".$db->escape($val).",%'";
 							$newres .= ')';
-							$i2++;
+							$i2++; // a criteria for 1 more field was added to string (we can add several citeria for the same field as it is a multiselect search criteria)
 						}
 					}
 				}
 			} else { // $mode=0
 				$tmpcrits = explode('|', $crit);
-				$i3 = 0;	// count the nb of valid criteria added for this field
-				foreach ($tmpcrits as $tmpcrit) {
+				$i3 = 0;	// count the nb of valid criteria added for the current couple criteria/field
+				foreach ($tmpcrits as $tmpcrit) {	// loop on each OR criteria
 					if ($tmpcrit !== '0' && empty($tmpcrit)) {
 						continue;
 					}
 					$tmpcrit = trim($tmpcrit);
 
-					if ($tmpcrit == '^$') {	// If we search empty, we must combined different fields with AND
+					if ($tmpcrit == '^$' || strpos($crit, '!') === 0) {	// If we search empty, we must combined different OR fields with AND
 						$newres .= (($i2 > 0 || $i3 > 0) ? ' AND ' : '');
 					} else {
 						$newres .= (($i2 > 0 || $i3 > 0) ? ' OR ' : '');
@@ -9927,15 +9926,15 @@ function natural_search($fields, $value, $mode = 0, $nofirstand = 0)
 
 					$i3++;
 				}
-				$i2++; // a criteria was added to string
+
+				$i2++; // a criteria for 1 more field was added to string
 			}
-			$i++;
 		}
 
 		if ($newres) {
 			$res = $res.($res ? ' AND ' : '').($i2 > 1 ? '(' : '').$newres.($i2 > 1 ? ')' : '');
 		}
-		$j++;
+		$i1++;
 	}
 	$res = ($nofirstand ? "" : " AND ")."(".$res.")";
 
diff --git a/htdocs/projet/list.php b/htdocs/projet/list.php
index 924930e14ac..0d75a0ce7f9 100644
--- a/htdocs/projet/list.php
+++ b/htdocs/projet/list.php
@@ -501,7 +501,6 @@ if ($search_opp_percent) {
 $sql .= dolSqlDateFilter('p.dateo', $search_sday, $search_smonth, $search_syear);
 $sql .= dolSqlDateFilter('p.datee', $search_eday, $search_emonth, $search_eyear);
 
-
 if ($search_date_start_start) {
 	$sql .= " AND p.dateo >= '".$db->idate($search_date_start_start)."'";
 }