Yeah, one line...
DateSerial(<year>, <month> + 1 , 0)
Example:
Dateserial("1999", "4", 0) = 3/31/1999
Dateseral function is pretty cool like that! When you place a "0" in the function, it always returns the last date of the previous month. To parse out the date itself, simply use the Month, Day, or Year function.
Gary
gwinn7