Visual Basic Form Validations

Hi,
How do i set the focus back onto a textbox
eg : I am using the following code in my Visual Basic project

If IsNumeric(txtJobCode.Text) Then
If txtJobCode.Text < 100 Or txtJobCode.Text > 174 Then
MsgBox "Please enter a number for JOBCODE between 100 and 174 only."
txtJobCode.SetFocus
End If
End If

I do get the message box but i never get the setfocus back onto the textbox
Please Help,
New to Visual basic.
PS : This is not VBScript in html but i am working on a visual basic project.