If it is a one-off thing your best bet would be to use a small piece of VBA
code that cycles through each cell, checks to see if the last character is
the letter A and truncates the contents of the cell by 1 character.
If you are comfortable with using VBA the code is simple.

The code below will cycle through each cell in the selected area and
truncate the cells that end in "A"

Just go into VBA editor, paste the code below then go to the sheet you want
checked, select the area you want and run the code. It is not very elegant
but should do the job for a one-off.
It works on Excel 2003, should work on others

SAVE THE SHEET FIRST! Preferably under a different name in case of problems.

Sub TruncateCells()

Dim rng As Range

For Each rng In Selection
   If Right(rng, 1) = "A" Then
       rng = Left(rng, Len(rng) - 1)
   End If
Next

End Sub

AndyW