Hi I have a question that kind of expands on this question:

I have workshops and individual sessions for that workshop in Salesforce. When a workshop is created I want the sessions to be created based on the information entered on the workshop record. I understand how to do this if the workshop meets just one day a week (see code below) but sometimes these workshops meet two or three times a week and the particular days are stored in a multi picklist. The user can select which days they meet, the start date, and the end date. 

I cannot for the life of me figure out how to create ongoing records for sessions occuring on, say, Mondays AND Thursdays AND Wednesdays or any other combo of days. Can anyone help?

trigger AssociatedSessions on Group__c (after insert) {

	List<Session__c> session = new List<Session__c>();
    
    for (Group__c newGroup: Trigger.New) {
            Date sd1 = newGroup.Start_Date__c;
            Date ed1 = newGroup.End_Date__c;
            
            if (newGroup.Frequency__c == 'weekly') {
                integer numberOfWeeks = sd1.daysBetween(ed1) / 7 ;
            
            	for(integer i = 1; i < numberOfWeeks ; i++){
              	  session.add (new Session__c(
                  Term__c = newGroup.Id,
                  Date__c = sd1 + i * 7)
                  );
                      
            	}   
  			}
        if (newGroup.Frequency__c == 'daily') {
            integer numberOfDays = sd1.daysBetween(ed1);
            
            for(integer i = 1; i < numberOfDays ; i++){
              	  session.add (new Session__c(
                  Term__c = newGroup.Id,
                  Date__c = sd1 + i * 7)
                  );
             }
        }
        if (newGroup.Frequency__c == 'biweekly') {
            integer numberOfDays = sd1.daysBetween(ed1) / 14;
            
            for(integer i = 1; i < numberOfDays ; i++){
              	  session.add (new Session__c(
                  Term__c = newGroup.Id,
                  Date__c = sd1 + i * 14)
                  );
             }
        }
        if (newGroup.Frequency__c == 'monthly') {
            integer numberOfDays = sd1.daysBetween(ed1) / 30;
            
            for(integer i = 1; i < numberOfDays ; i++){
              	  session.add (new Session__c(
                  Term__c = newGroup.Id,
                  Date__c = sd1 + 30)
                  );
             }
        }
        
    insert session;
 	}
}