I'm not sure what your first question is - does the SP formula not
work, then? Check the formatting of column A (dates?) and column D if
not.

For your second question, you can just reformat the cells using a
custom format of mm yyyy, or mmm yy, or mmmm yy. (3 m's will give the
abbreviated name, 4 m's will give the full name)

Alternatively, you could put:

=A1

in an adjacent cell, format this as mm yyyy (or one of the others),
and copy down.

Another alternative still is to use this formula:

=TEXT(A1,"mm yyyy")

and copy down, although this will return a text result.

Hope this helps.

Pete

I'd use:
=SUMPRODUCT(--(text($A$18:$A$3295,"yyyymm")=text($C4,"yyyymm")),
           --($D$18:$D$3295>=1000))

Where C4 contains a real date, too.