InfoPath Dev

Hi, I'm working on a Expense Report form in InfoPath, and I need to sum a field in a repeating table meeting a criteria -Déjà vu- I need to sum the 'Amount' only when the 'Payment' = "Personal Funds" Last time I had that problem, I used the Sum and Eval functions. So far this is the formula I have: sum(xdMath:Eval(../my:group2/my:group3/my:Payment[. = "Personal Funds"], ../my:group2/my:group3/my:Amount)) This is the error I'm receiving: Type mismatch. Error occurred during a call to property or method 'Eval'. Can you guys help me come up with the right formula syntax?

I found it!! sum(xdMath:Eval(../my:group2/my:group3[my:Payment = "Personal Funds"], "my:Amount"))