I need to write code in Visual Basics 2012 for a grading system. I can do most of it but I don't know how to make it see missing grades. Also when they fail a grade the background turns red but when I clear the boxes it stays red this is my clear:

Question

I need to write code in Visual Basics 2012 for a grading system.  I can do most of it but I don't know how to make it see missing grades.  Also when they fail a grade the background turns red but when I clear the boxes it stays red this is my clear:

Private Sub btnClear_Click(sender As Object, e As EventArgs) Handles btnClear.Click
        Test1.Clear()
        Test2.Clear()
        Quiz1.Clear()
        Quiz2.Clear()
        Quiz3.Clear()
        Assignment1.Clear()
        Assignment2.Clear()
        Assignment3.Clear()
        Assignment4.Clear()
        Assignment5.Clear()

Thanks