[AccessD] How do I pass a control to a function in the Control Source

I want to send a control object to a function from the ControlSource of a
text box.

I can send the Form object, but how about the control?

 

.

Example:
Let's say I want to send a control's tag to a function 
The name of the control is "txtFinalCalculation",
This in fact does work:
=GetTestResults([txtFinalCalculation].Tag)

The function retrieves the tag value with a function like: 
Function GetTestResults(strTagValue as string)

But I had to include the control's name in the original call. I want it
generic.

Something like:
=GetTestResults(ThisControl)

Then use the following function:
Function GetTestResults(ctlControl as control)

I've tried some things with "Active control " but that won't work.
There has to be a way to send the control's info to a function.
I can send the Form's properties: GetTestResults([Form]), but I want just
the individual control.