Assuming you have opposite sign (say, credit as positive and debit as
negative) then check out the help entry for Format, particularly number
formatting and custom formats.  You can define a format that includes literal
characters, so if you display the results in a text box that is wider than
necessary and include something like a tab character (Ascii code 9), you can
offset debits to what looks like a separate column.

Alternatively, provide two text boxes, each bound to the transaction amount
but using a calculated control source value something like:

Credits
   = iif([Value] >=0, [Value], Null)

Debit
   = iif([Value] < 0, [Value], Null)

Hope that helps