I will take your question to mean that you want to display
only, not store the values. Create two text boxes on the
form, named txtOne and txtTwo. Right click each, and
select Properties. Click the Format tab, click in the
Format line, click the down arrow, and select General
Number. Create a third text box. Select Properties as
above. Click the Data tab, and in Control Source enter
(without the quotes) "= txtOne] + [txtTwo]".
Another approach is to go to the form's underlying table.
In design view, create fields One and Two. Set the Data
Type to Number (Long Integer in Field Size is OK). Back
to the form, set the Control Source (as above) of txtOne
to One, of txtTwo to Two (use the down arrow to select the
field). Leave the third text box as it is.
There are other possible answers as well, such as
calculate queries. You might need to provide some more
details of what you need to do. Remember that if this is
stored data you will probably want to store the individual
numbers that are added together, not the sum.