Hi Shaik,
I have done this functionality in my org, with the help of apex trigger.
This is the following code to achieve this functionaity.
trigger toCheckNumberOfUser On Opportunity(before Insert, before update){
Map<Id,Integer> mapofOwnerIdVsCount = new Map<Id,Integer>();
for(AggregateResult arOpp : [select count(id),OwnerId from Opportunity Group BY OwnerId HAVING Count(id)>0] ){
mapofOwnerIdVsCount.put(Id.valueOf(String.valueOf(arOpp.get(‘OwnerId’))),Integer.valueOf(arOpp.get(‘expr0’)));
}
for(Opportunity opp: Trigger.new){
if(mapofOwnerIdVsCount.get(opp.OwnerId)>15){
opp.addError(‘Number of Opportunity on this User is greater than 15’);
}
}
}
Thanks