Validating Event VB.net

[jenbug]

Alright, I have read and searched but I dont understand what a validating event is and how I use it for this program. Basically, I am trying to make sure that text in 3 dif textboxes is btween 0 and 100 and if its not, I need to change the forecolor to red . Can someone let me know if I am on the right track? My prob. right now is changing the forecolor.
Thanks
Jen

Private mblngrade As Boolean
    Private Sub CalcButton_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles CalcButton.Click
        'declare variables
        Dim decTest1, decTest2, decTest3, decAverage As Decimal
        Dim strID, strName, strGrade As String
        Dim blnGrade As Boolean
        'assign value to variables
        decTest1 = Val(Me.Test1TextBox.Text)
        decTest2 = Val(Me.Test2TextBox.Text)
        decTest3 = Val(Me.Test3TextBox.Text)
 
        strID = Me.IDTextBox.Text
        strName = Me.StudentTextBox.Text
        mblnGrade = ValidGrade(decTest1, decTest2, decTest3)
        decAverage = (decTest1 + decTest2 + decTest3) / 3
        'display Grade
 
        If blnGrade = True Then
            Me.AverageDisplay.Text = decAverage
        Else
            MessageBox.Show("This value must be between 0 and 100.", "Average", _
            MessageBoxButtons.OK, MessageBoxIcon.Information)
        End If
    End Sub
 
    Function ValidGrade(ByRef dec1 As Decimal, ByRef dec2 As Decimal, ByRef dec3 As Decimal) As Boolean
        'delcare varaible for boolean value
        Dim blnGrade As Boolean
 
        If dec1 >= 0 And dec1 <= 100 Then
            If dec2 >= 0 And dec2 <= 100 Then
                If dec3 >= 0 And dec3 <= 100 Then
                    Return True
                Else : Return False
                End If
            End If
        End If
 
    End Function
 
 
 
 
 
    Private Sub ClearButton_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles ClearButton.Click
        'clear the textboxes
        Me.StudentTextBox.Text = ""
        Me.IDTextBox.Text = ""
        Me.Test1TextBox.Text = ""
        Me.Test2TextBox.Text = ""
        Me.Test3TextBox.Text = ""
        Me.AverageDisplay.Text = ""
        Me.GradeLabel.Text = ""
    End Sub
   
    'Validate TextBoxes and change forecolor to red if data is invalid
    Private Sub Test1TextBox_Validating(ByVal sender As Object, ByVal e As System.ComponentModel.CancelEventArgs) Handles Test1TextBox.Validating, Test2TextBox.Validating, _
    Test3TextBox.Validating
        If mblngrade = True Then
            e.Cancel = False
        End If
    End Sub
 
    Private Sub ExitButton_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles ExitButton.Click
        Me.Close()
    End Sub
End Class