SUMIF

[Menachem Bazian]

Hi,

I was wondering if anyone can help me with this syntax. I have three 
tables, INVOICES, CHECKS and CHECK_APPLICATIONS. I need to SUM the 
amounts in CHECK_APPLICATIONS for each invoice IF the check it is 
related to has not been voided. Something like this (in SQL and pseudocode)

SELECT invoices.id, invoices.vendor, invoices.namount AS 
nninvoiceamount, SUM(check_applications.namountapplied IF checks.lvoid=0)

I also need to refer to that SUM in another field.

invoices.namount - SUM(namountapplied we did before) AS namountleft

Any ideas?