Expression creates #name? errors

[Rats]

I am creating a form with a subform. I have a subtotal on the sub form which I wish to display on the main form and perform a calculation. However, when I create the text box and set it's Control Source to the address of the subform total I keep getting #name? errors. I have checked the code & it seems to be correct but nothing seems to work. I have copied existing working text boxes to this form and they don't work. Is it possible for a form to have some setting that prevents reference to another form in an expression. By the way I used the expression builder to create the sources. The expression looks like this.
=[Forms]![Order Details Sub Form]![TotalSales]. Hope someone can help.

Thanks

 

[maxmangion]

take a look at this thread

 

[Rats]

Thanks will do.