TextBox Casting and Validation

Hi,

I have got 4 texboxes which should handle Double type numbers. At the access database in the back-end, I created them as Text data type. The program needs to multiply those 4 values to get a desired number. My 2 questions are:

1. I am trying to do the multiplication on the change handle of every text box, but I get an error which states that “Cast from string”” to type ‘Double’ is not valid”. I made sure that the initial value of the text box is not empty but I am not successful.

2. What is the best way to force the user to enter the numbers in a fraction format i.e. 0.XXXX. Because if a whole number is entered it would mess up the whole calculation.

Appreciate your help on this because I am new to VB.NET

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