Modules & VBA :: Current Checkbox Label Update

I have the following module which displays the backcolor of a checkbox label if it is true or false

Private Sub FormatLabel(chk As Control)
With chk.Controls(0)
If chk Then
.BackColor = vbYellow
.BackStyle = 1
.ForeColor = vbRed

[Code] .....

Which works great! But I cannot figure out how to make it work in the control AfterUpdate Event. I tried using it in the current control's (checkbox) after update event

Dim itm As Control
If itm.ControlType = 106 Then FormatLabel itm

but nothing happens (no change, no error message).

I have tried creating a new module:

Public Sub CheckBoxFormat(chk As Control)
If chk = -1 Then
chk.BackColor = vbYellow
chk.BackStyle = 1
chk.ForeColor = vbRed
Else
chk.BackColor = vbWhite
chk.ForeColor = vbBlack
End If
End Sub

But when I try to call it in the AfterUpdate event for the particular checkbox

Private Sub CheckBoxA_AfterUpdate()
Dim itm As Control
If itm.ControlType = 106 Then
CheckBoxFormat itm
End Sub

I get the error message "Expected Variable or Procedure not module"

So, (1) is my module all wrong or (2) am I calling it incorrectly or (3) wrong on both items?