Question : Sum Group Footer using textbox reference instead of Field reference

I am trying to put a sum in a group footer by referencing the textbox name instead of the value of the Field.  The reason for doing this is that two different values are going into the same field in the database, depending upon another field.

Eg.
Field1       Field2
10,000     Y
-9,000      N
2,000       Y

I want to sum Field1 where Field2 = Y

If anyone can think of a different way, I'm ready to try it!!

Many thanks in advance

Answer : Sum Group Footer using textbox reference instead of Field reference

Thanks for the suggestion martenrune

Got it sorted by using a CASE statement in my original sql:
CASE Field2
   WHEN Y THEN Field1
   ELSE 0
END FieldA,
CASE Field2
   WHEN N THEN Field1
   ELSE 0
END FieldB,

This created two new fields, which I can sum etc