Trigger OpptyTeamLock on OpportunityTeamMember (Before Insert,Before Delete){
set<Id> oppIdSet = new set<id>();
    If(Trigger.IsBefore){
        If(Trigger.IsInsert){
            for(OpportunityTeamMember otm : trigger.new){
            oppIdSet.add(otm.OpportunityId);
            }
}
        If(Trigger.IsDelete){
            for(OpportunityTeamMember otm : trigger.old){
            oppIdSet.add(otm.OpportunityId);
            }
            }
    }
   // Id userid=UserInfo.getUserId();
    List<user> userinformation=[select id,commission_Admin__c from user where id=:UserInfo.getUserId()];
    list<Opportunity>lstOpp = [select Id,Name,Opportunity_Team_Locked__c from opportunity where Id In :oppIdSet and Opportunity_Team_Locked__c = true];
    If(Trigger.IsBefore){
        If(Trigger.IsInsert){
            for(OpportunityTeamMember otm : trigger.new){
                if(lstOpp.Size()>0 && userinformation[0].commission_Admin__c==false){
                otm.AddError('Error Message');
                }
            }
        }
        If(Trigger.IsDelete){
            for(OpportunityTeamMember otm : trigger.old){
                
                if(lstOpp.Size()>0 && userinformation[0].commission_Admin__c==false){
                otm.AddError('Opportunity Team is locked. Contact Commission Team');
                }
            }
        }
    }
}