Running the following macro will do it for the first table in the document:

Dim A As Range
Dim B As Range
Dim i As Long
With ActiveDocument.Tables(1)
For i = 1 To .Rows.Count
Set A = .Cell(i, 1).Range
Set B = .Cell(i, 2).Range
A.End = A.End - 1
B.End = B.End - 1
.Cell(i, 3).Range.InsertBefore Val(A) + Val(B)
.Cell(i, 4).Range.InsertBefore A - B
Next i
End With

I don't know why to get the sum it is necessary to convert the data in the
first and second columns to values. If that is not done, the data is
concatenated rather than summed. If handles the difference correctly
however without such conversion.

--
Hope this helps.

Please reply to the newsgroup unless you wish to avail yourself of my
services on a paid consulting basis.

Doug Robbins - Word MVP

"Tablequery" wrote in message
...
I have a WORD2003 table -- with 4 columns (A, B, C, and D) and 500 rows --
with numbers in each cell in Columns A and B. How can I show the SUMs (An
+
Bn) in Coulmn 3 and the DIFFERENCEs (An - Bn) in Column 4?

Is there a way to do all the 500 sums (or differences) with just a few
keystrokes or do I have to repeat the basic calculation 500 times?

Thanks. ...wdc