Add a calculated field to your query.
Field: CountYesForA: Abs(Sum(FieldA))
Group By: Expression
To start at the beginning,
open your query (assume you have one) in the grid design view
Select View: Totals from the menu - a new line will appear in the grid area.
The line will be titled Totals and will default to GROUP under every field
Insert "CountYesForA: Abs(Sum(FieldA))" (NO QUOTE MARKS) into a blank field
Select Expression for it in the Totals line