I need to copy a formula from column I to column J, and would like to do the
following:
Column I                         Column J
=SUM((APR!C4))              =SUM((MAY!C4))

Basically, when I copy I would like to add 1 month, but leave the cell (C4)
the same. When I try it, the month always stays the sam, but the cell changed
from C4 to D4. I would like to know how to copy the above forumula in Colum I
so the result will be the formula above in Column J.

Thank you for any help.
Simon