Refer to the control as you would a Subform.
You were almost correct with the third try listed above.

=[Forms]!Event-MainF]![Event-NonMemF].[Form]![TotNonMem]

Value From a Form
Value From Subform

Makes Sense, Thanks.

So just refer to these as if they were a subform, and not as their tab control name.

Indeed, the tab control isn't really a container in the sense that it doesn't hold the controls inside it like a subform would. It's more of a mechanism to manage the visibility of controls on your form. These controls are just placed on the form and the tab control helps to show or hide them as needed. And did I mention I really hate tab controls? :)

Kevin, I gave it a try, did have to make one tiny change and add the [

=[Forms]![Event-MainF]![Event-NonMemF].[Form]![TotNonMem]

but I'm still getting a #Name? error the forms and field are spelt correctly

Rick do they rank up there with split forms??? lol

Hi Jerry, make sure you reference not the tab's name, but the actual subform control's name.  See picture below.  All the tabs have their own names, and that's one of the reasons Richard (and other users) dislike them.  It's a confusing system.  Tabs have names so you can set their focus.  But you should use the name of the subform control inside the tab in references.

Here are screenshots of the form and the field. I can send anything you might require.

This is my last form to use the Tab Controls, I have switched all my others over to using something like this

SubFormCTL.SourceObject = "MembershipF"

I'll get to this one eventually.  Sorry to be such a bother

In your third screenshot, I see that the Non-Members form seems to have AllowAdditions set to false (it doesn't have a blank line to add a new record).  If that form has no record, it will be totally empty, and the record selector that normally shows "n of n" will be *blank* (see picture below).  In that case, the form will behave as if the whole form doesn't exist.  Anything you put in the footer will also be considered nonexistent.  That may be why you get an error when you try to reference that control elsewhere.  The Count() function will not give you zero, because it is not evaluated -- because the control itself is considered nonexistent.  This has to do with how forms work, and nothing to do with tab controls.  Please confirm if this is in fact what you are seeing.  Then we will think of a solution.

Thanks ever so much for the effort I must have something else set wrong as I did change the for to allow Additions and even set the default value to Zero.  The counter is working on the Non Members tab. I'm going to break down and redo the form to use the SubFormCTL.SourceObject = like my other forms.  I see why Rick does not like to use them.  I won't take up any further time on this you can close it.

OK, I don't know why I didn't do this in the first place.

=DCount("MemID","NonMemT","EventID =" & EventID

It's one of those "step back ask 5 people and then leave it for a day and come back to it" kind of things I guess.

That's OK. That's what you're here for... to learn.