=SUMPRODUCT(--NOT(ISBLANK(Q8:q300)),F8:F300)

or

=SUM(--NOT(ISBLANK(Q8:q300))*F8:F300)

In the second case you needed to multiply. Also the second formula
needs to be array-entered (Ctrl+Shift+Enter)

HTH
Kostis Vezerides

On Mar 1, 5:21 pm, Lisa wrote:
ACTUALLY, it's not working. I tried the following:

=SUM(--NOT(ISBLANK(Q8:q300)),F8:F300)

and the formula is calculating the sum of column F but disregarding the
condition. IOW, it's ignoring if it's a blank cell or not. Sugesstions??