Pivot Table - if Formula

[Sabine]

I'd like to add a formula to my pivot table, that sums the $s for Period 1
through 8 if the account # is above 4000 and sums the $s for PY + P1 through
8 if the account # is below 4000.
I wrote the formulas as
if(account #<4000, PY+P1+P2+P3+P4+P5+P6+P7+P8,P1+P2+P3+P4+P5+P6+P7+P8)
but it doesn't seem to recognize the account number because it returns the
"false" portion of the formula
I tried grouping the account numbers into group 1 and group 2 and changed
the formula to
if(account #2="group 1", PY+P1+P2+P3+P4+P5+P6+P7+P8,P1+P2+P3+P4+P5+P6+P7+P8)
but had the same problem.
Thanks for the help.
Sabine