Gazza,
Try this....
if month(currentdate) = 12 then
dateserial(year(currentdate)+1,01,01)
- currentdate
else
dateserial(year(currentdate),month(currentdate) + 1,01)
- currentdate
You will be counting the number of days to the first day of next month unless its December when you will count upto the 1st of January of the next year.