1) In your Dim statement, "Value" is not a valid data type.
2) You are setting c and d "Value" variables to a Format result, which is a text string.
3) "Number" is not a valid predefined format type that can be used with the Format command
Your code would fail for any of these 3 reasons...
If you dimension the variables properly and make valid use of the Format command you can add textboxes values together without too much difficulty.