Как запустить процесс из TextBoxa

Private Sub txtDestin1_KeyDown(KeyCode As Integer, Shift As Integer)
KeyDown = True
Dim z As Integer, x As Integer, y As Integer
x = txtZona1.Text
y = txtZona2.Text
z = y - x
txtDestin1.Text = z
End Sub

'поставь Form.KeyPreview=True
 
Private Sub Form_KeyDown(KeyCode As Integer, Shift As Integer)
Dim z As Integer, x As Integer, y As Integer
if KeyCode=vbkeytab or keycode=vbkeyreturn then
 if isnumeric(txtZona1.text) and isnumeric(txtZona2.text) then
   x = txtZona1.Text
   y = txtZona2.Text
   z = y - x
   txtDestin1.Text = z
 end if
end if
End Sub

Private Sub Calculation()
Dim z As Long, x As Long, y As Long
x = txtZona1.Text
y = txtZona2.Text
z = y - x
txtDestin1.Text = z
End Sub

Private Sub txtDestin1_GotFocus()
    Calculation
End Sub

Private Sub Form_KeyDown(KeyCode As Integer, Shift As Integer)
    If KeyCode = 13 Then
        Calculation
    End If
End Sub

Private Sub Form_KeyUp(keyCode As Integer, Shift As Integer)
If IsNumeric(txtZona1.Text) And IsNumeric(txtZona2.Text) Then
If keyCode = vbKeyReturn Or vbKeyTab Then
Calculation
End If
End If
End Sub
 
Private Sub Text3_GotFocus()
Calculation
End Sub
 
Private Sub Calculation()
Dim z As Integer, x As Integer, y As Integer
x = txtZona1.Text
y = txtZona2.Text
z = y - x
txtDestin1.Text = z
End Sub