TOP N problem with GROUP BY clause

The problem: I need to find all active [GiftPledges] that have the last three [GiftDetails] have a zero amount.

SELECT gp.PledgeId FROM GiftPledge gp
      INNER JOIN GiftDetail gd ON gp.PledgeId = gd.PledgeId
      WHERE gp.PledgeStatus = 'A'
      GROUP BY PledgeId
      HAVING COUNT(PledgeId) >= 3

Now, I have all my [GiftPledges] that have at least three [GiftDetails].

SELECT TOP 3 gdi.Amt FROM GiftDetail gdi
      INNER JOIN GiftHeader ghi ON gdi.GiftRef = ghi.GiftRef
      WHERE gdi.PledgeId = gp.PledgeId
      ORDER BY ghi.GDate DESC

This gives me the three most recent [GiftDetails] associated with a given [GiftPledge]. The problem is that I don't know how to sum the second query and have it be a part of the WHERE clause in the first query.

I found this article about "Top n per Group" and that seems like the direction I need to be headed, but I'm not sure I'm on the right track.

Any help, clarifications or suggestions would be greatly appreciated.

From stackoverflow

• SELECT gp.PledgeId FROM GiftPledge gp
        INNER JOIN GiftDetail gd ON gp.PledgeId = gd.PledgeId
        WHERE gp.PledgeStatus = 'A'
        GROUP BY PledgeId
        HAVING COUNT(PledgeId) >= 3 
  AND
  GP.PledgeID in (
  SELECT PledgeID From
  (
  SELECT TOP 3 gp.PledgeID, gdi.Amt  FROM GiftDetail gdi
        INNER JOIN GiftHeader ghi ON gdi.GiftRef = ghi.GiftRef
        WHERE gdi.PledgeId = gp.PledgeId
        ORDER BY ghi.GDate DESC
  ) x_amt 
  Group By PledgeID
  Having SUM(AMT) ) x_sum = 0
  

  something like that anyway.