ASP gridview: adding two values and validate

Question

I use GridView to show/edit data in the database. In the GridView there are two columns called mark1 and mark2. What I want to do is when user clicks update, the program should check if the values entered at mark1 and mark2 sum to 100. If they don't the program should cancel the update and show an error message. How do I do it? I use ASP.NET with VB.

Answer 1

take a look at custom validation control. if you provide some code, i can fix it for you if it doesn't work.