Calculate % of Total per group

Hi All,

I have a report that groups Agents by a call group, and shows the total for each call group in the Call Group header row, then agent totals in the detail row.  This works fine ... where I am running into trouble is showing the % of total calls each agent has taken for thr group.  See my sample below:

========================================
Call Group 8000           200 Calls
  -Agent 2000                 25 Calls
  -Agent 2001               150 Calls
  -Agent 2002                 25 Calls

Call Group 9000           150 Calls
  -Agent 3000                 75 Calls
  -Agent 3001                 75 Calls

So basically, in the RDL, I want to calculate the % that each Agent took for the group.  Somehow I need to get that group total into the detail records, without editing the query passing in the data.  In other words, for Agent 3000, I need to somehow say 75 (Agent 3000 Calls) / 150 (Group 9000 Calls) = 50%.  

I am having trouble getting the Group Total (150) value from the detail row.

Thanks in advance for any help!
-Matt