How to pass a TextBox

Dear Forum Members

I need to change the Font and color of one or all of several textboxes if they have been left blank.
I had hoped to do this by refering to a proceedure using code like this:_

If tbWidth.value="" Then
Call ChangeFont(tbWidth)
End If
End Sub
Sub ChangeFont(MyTextBox as TextBox)
MyTextBox.Text="***"
MyTextBox.Font=14
MyTextBox.ForeColour=vbRed
End Sub

Using tbWidth, Me.tbWidth, .tbWidth in the Call line all give error messages.
The code in Sub ChangeFont works if written directly in the calling procedure
Can anyone help please
Ems