you don't enter calculations in table fields. normally, you also don't save
the results of calculations in table fields. instead, you save the raw data
in one or more tables, then create a calculated field in a query to display
the value, as

   C: A + B

hth

The best way to accomplish your goal is to place Columns
A and B into your table. Then, create a query with a
calculated column: For example,
TableNew
FieldA:
3
44
FieldB:
5
10
Now create a query that pulls both fields and place your
calculated field in the 3rd column of the query: Say for
example: MyCalcField:[FieldA] + [FieldB](This would be
typed into the top row of column 3 in the design grid of
the query exactly as above. When you run the query, each
row will calculate the MyCalcField value.It would look
like this:
FieldA     FieldB     MyCalcField
3          5          8
44         10         54