Preserve the position of User Forms VBA - forms

Question

I'd like to preserve the position of a number of forms in the centre of the application, forms will be different sizes so below FormTop/FormLeft snippet can't be run again and again with the same effect. To do this I'm setting a public variable with the form's .top and .left values.
I get an error "Object Doesn't support this property or method", which seems odd as I was under the impression that the equation to make FormLeft would evaluate to a double data type. Both the lines work fine in the second section of code, what am I doing wrong?
Public FormTop As Double
Public FormLeft As Double
sub main()
CentreForm UserForm2
end sub
Sub CentreForm(UForm As UserForm)
With UForm
If FormTop = 0 And FormLeft = 0 Then
'*********Errors appear on the below two lines******************
FormLeft = Application.Left + (0.5 * Application.Width) - (0.5 * .Width)
FormTop = Application.Top + (0.5 * Application.Height) - (0.5 * .Height)
Debug.Print FormLeft, FormTop
End If
.StartUpPosition = 0
.Left = FormLeft
.Top = FormTop
End With
End Sub
sub IWork()
With UserForm2
.Left = Application.Left + (0.5 * Application.Width) - (0.5 * .Width)
.Top = Application.Top + (0.5 * Application.Height) - (0.5 * .Height)
end with
end sub

Answer 1

If you can't solve your problem based on comment suggestion please change this line:
Sub CentreForm(UForm As UserForm)
into
Sub CentreForm(UForm As Object)