Thanx for your reply.Let me tell you in detail that what i want to do with this Trigger.

trigger SessionCapacitychange on Session__c (after update)
{
    if (Trigger.isAfter && Trigger.isUpdate)
    {
        List<Wait_listed_Registrant__c> WaitLst = new List<Wait_listed_Registrant__c>();
        List<Wait_listed_Registrant__c> WaitLstdelete = new List<Wait_listed_Registrant__c>();
        List <Session_Attendance__c> sessAttdList = new List <Session_Attendance__c>() ;
           List<Wait_listed_Registrant__c> delWaitLstdelete = new List<Wait_listed_Registrant__c>();
        List<Session_Attendance__c> insertsessAttdList = new List <Session_Attendance__c>() ;
        List<Session__c> sessList = new List <Session__c>() ;
        List<Id> SessId = new List<Id>();
        
        for(Session__c Sess : Trigger.new)
        {
            
            if(Sess.Capacity__c > Trigger.oldMap.get(Sess.Id).Capacity__c)
            {
                   SessId.add(Sess.Id);
            }
        }
        WaitLst = [select Id,Registration__c from Wait_listed_Registrant__c where Session__c in:SessId order by CreatedById DESC];
        
        for(Session__c Sessn : Trigger.new)
        {    
            double balancesize = Sessn.Balance__c;
            //system.debug('balancesize.....'+ balancesize);
               
            Integer loopCount = balancesize.intValue();
                        //system.debug('balancesize------------------------------------------------->>'+balancesize);                
            if(balancesize>WaitLst.Size())
            {
                  loopCount = WaitLst.Size();
            }
                        // system.debug('WaitLst[1].Registration__c'+WaitLst[1].Registration__c);
            Integer SessionMovedCount =0;    // system.debug('WaitLst[0].Registration__c'+WaitLst[0].Registration__c);
            for(Integer i=0;i<loopCount;i++)
            {
                system.debug('values.....'+ balancesize);
                if( WaitLst!=null && WaitLst.Size()>0 )
                {                  
                    Session_Attendance__c s = new  Session_Attendance__c();
                    s.Registration__c = WaitLst[i].Registration__c;
                    s.Session__c= Sessn.Id;
                    s.Status__c = 'Registered' ;
                    SessionMovedCount = SessionMovedCount +1;
                      sessAttdList.add(s);
                      WaitLstdelete.add(WaitLst[i]);
                      
                }    
                else if(WaitLst==null && WaitLst.Size()<=0)
                {
                    system.debug('WaitList is empty');
                }                                                                
            }
                
               //system.debug('values...........'+sessAttdList);
            if ( sessAttdList.size() > 0 )
                insertsessAttdList = sessAttdList;
              
            if(WaitLstdelete.size() > 0 )
                
                delWaitLstdelete = WaitLstdelete;
             
            if(insertsessAttdList.size() > 0 )
            {                        
                Session__c s = new Session__c(Id= Sessn.Id);
                Double value = 0;
                if(s.Used__c!=null)
                {
                     value = s.Used__c;
                   }    
                value  = value +  insertsessAttdList.Size();
                s.Used__c = value;
                sessList.add(s);
                  
             }          
        }            
         
           insert insertsessAttdList;
        delete delWaitLstdelete;
        update sessList;
    }

}

This is my Trigger. As you can see that this Trigger will fire on update of my custom Object.
Session__c Object having two Child Objects ---- Session_Attendance__c & Wait_listed_Registrant__c
If i change the capacity of Session then according to balance it will Delete the Waitlist records & according to that it will insert same number of records in SessionAtteendence Object.

The trigger work fine if waitlist got less then 50 records...means total number of DML records processed are less then 100
But if waitlist got more then 50 records it throw an exception...... TOO MANY DML ROWS
like if waitlist got 60 records
it will show ....TOO MANY DML ROWS:120              ( 60 for insert + 60 for delete)

i have followed every rule of best Practices.. please have a look at the code & let me know how to solve this issue.
i have tried it through class & used tht function in class , i tried web service.. but it did nt work

Help needed

Regards;
AKash (Salesforce.com Developer)