How can I fix my timer algorithm problem?

I wish to find the problem of this code which gives that the application is in break mode Exception unhandled. What can I try?

System.InvalidOperationException occurred HResult=0x80131509 Message=An error occurred creating the form. See Exception.InnerException for details. The error >> > is: Object reference not set to an instance of an object. Inner Exception 1: NullReferenceException

Code:

Public Class Form1
    Dim h As Integer = 0, h2 As Integer = Val(TextBox1.Text)
    Dim m As Integer = 0, m2 As Integer = Val(TextBox2.Text)
    Dim s As Integer = 0, s2 As Integer = 60
    Dim m1 As Integer = 0, ml2 As Integer = 100

Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
        Timer2.Start()
    End Sub
Private Sub Button2_Click(sender As Object, e As EventArgs) Handles Button2.Click
        Timer2.Stop()
    End Sub

Private Sub Button3_Click(sender As Object, e As EventArgs) Handles Button3.Click
        Timer2.Stop()
        h2 = Val(TextBox1.Text)
        m2 = Val(TextBox2.Text)
        s2 = 60
        ml2 = 100
        Label1.Text = h2 & " : " & m2 & " : " & s2 & " : " & ml2
    End Sub

Private Sub Timer2_Tick(sender As Object, e As EventArgs) Handles Timer2.Tick
        ml2 -= 1
        Label1.Text = h2 & " : " & m2 & " : " & s2 & " : " & ml2
        If ml2 = 0 Then
            ml2 = 100
            s2 -= 1
            Label1.Text = h2 & " : " & m2 & " : " & s2 & " : " & ml2
            If s2 = 0 Then
                s2 = 60
                m2 -= 1
                Label1.Text = h2 & " : " & m2 & " : " & s2 & " : " & ml2
                If m2 = 0 Then
                    m2 = 60
                    h2 -= 1
                    Label1.Text = h2 & " : " & m2 & " : " & s2 & " : " & ml2
                    If h2 = 0 Then
                        h2 = 0
                        Timer1.Stop()
                        h2 = Val(TextBox1.Text)
                        m2 = Val(TextBox2.Text)
                        s2 = 60
                        ml2 = 100
                        Label1.Text = h2 & " : " & m2 & " : " & s2 & " : " & ml2
                    End If
                End If
            End If
        End If
    End Sub
End Class

You can not access value of TextBox1 before complete initialization. Just by tweak your code slightly, error goes away.

Dim h As Integer = 0, h2 As Integer = 0
Dim m As Integer = 0, m2 As Integer = 0
Dim s As Integer = 0, s2 As Integer = 60
Dim m1 As Integer = 0, ml2 As Integer = 100

Set h2 and m2 value at load event of form like as below:

Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load       
    h2 = Val(TextBox1.Text)
    m2 = Val(TextBox2.Text)
End Sub