Something

while($row = mysql_fetch_array( $result )) {
	$ReminderArray = explode("|", $row['ReminderCalls']); //reminder calls is  equal to something like 1|3|5|7| 

    $x = count($ReminderArray); 
	$i = 0;
		
while ($i < $x) {

if (isset($ReminderArray[$i])) {	
				
//i get a notice saying day is undefined, but it should be day1 day3 day5 day7 etc
 					if ($_POST['day'.$ReminderArray[$i]] <> 1) { 
 						
						$OneDayBefore = $_POST['day'.$ReminderArray[$i]]-1;
 						$DayBefore = $OneDayBefore."/".$_POST['month'.$ReminderArray[$i]]."/".$_POST['year'.$ReminderArray[$i]]; 
						
 					} else if ($_POST['month'.$ReminderArray[$i]] <> 1) {
 							switch ($_POST['month'.$ReminderArray[$i]) {
								case 5:
								case 7:
								case 10:
								case 12:
									 $OneDayBefore = 30;
								break;
								case 2:
									 $OneDayBefore = 28;
								break;
								default:
									 $OneDayBefore = 31;
								break;
							};
 						 $OneMonthBefore = $_POST['month'.$ReminderArray[$i]]-1;
 						 $DayBefore = $OneDayBefore."/".OneMonthBefore."/".$_POST['year'.$ReminderArray[$i]]; 
 
 					} else {
 
 						 $OneYearBefore = $_POST['year'.$ReminderArray[$i]]-1; 
						 $DayBefore = "31/12/".$OneYearBefore;
 					};
			

			
			
		$i++;

mysql_query("INSERT INTO jobs (JobDueDate, JobCode, JobCourseCode, JobComplete) 
                             VALUES ('".$DayBefore."', '1', '".$CourseCode."', 'FALSE')") 
	 or die(mysql_error()); 
};
}; 
};