Hi!
Sorry to barge in, but it seems your textboxes contains text, and not numbers. So the result is a concatination of the text, and not the sum of the numbers.
Either go to the table and change from text to numbers, or do conversion. For instance, if those numbers cannot be negative and less den 255, try:
=cbyte(r1)+cbyte(r2)+cbyte(r3)+cbyte(r4)
For larger numbers cint, clng, for decimals csng, cdbl (check out the help on these functions)