If you want to stop the User from going to the 2nd field on your Input Form if the first field is not filled in - what you can do is put some code in the GotFocus event of the second field of your Form - something like this:
Code:
Private Sub ControlName2_GotFocus()
Me.ControlName1.SetFocus
If Me.ControlName1.Text = "" Then
MsgBox "Please enter a value in the Text box."
Me.ControlName1.SetFocus
End If
End Sub
What I sometimes do, is to put the Code in the 'Save' or 'Submit' button of the Form and then check all the fields to make sure they have legitimate values . . .
Hope this helps!!