Yep, Bob took this where I was going with it. Only one other thing I would add though. I think you want to check to see if the value in Submitted is Null before you default it. Otherwise, if you enter something so both get populated, and then go back and want to change the Total value, the Submitted amount will change automatically too, even if you do not want it to. To prevent that, your code would look something like:
Code:
Private Sub txtTotal_AfterUpdate()
If IsNull(Me.txtSubmitted) Then
Me.txtSubmitted = Me.txtTotal
End If
End Sub