Percent difference in a subgroup

Hi, yes i am back again, percentages on groups and subgroups

In my previous post i was able to deliver a total percentage (script after image), this is great, now i am struggling with this as a subtotal in each CurrentPriority,and then i need to give a break down of percentage for each category, i may have my table structure wrong.

So i have a total in the Patient Count Over Boundry, i want in the % Over Boundry by group of the Total WaitList Count..

Example: Cardiology 2-Semi Urgent = Total 7 and TotalWaitListCount= 56

Calculate 7/56*100

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=Sum(Count(IIF(Fields!OverBound_Flag.Value="Yes",0,Nothing)))/(Sum(Count(Fields!WaitingListId.value)))

David