can you post your config?

where exactly have you placed that formula? into 'Default value'?

if so, then it is evaluated just in NEW mode and just at form load...

how do you test it?

Here is the Single Line Textbox:

Below is the form and the "True" single line of text is the isAdmin field.

As you can see, I currently am in the ADMINS group right now.

Once I remove myself from the ADMINS group and go back into the form, it still says True so it's not refreshing based on who is in the ADMINS group.

Once I remove myself from the ADMINS group and go back into the form

what exactly means 'go back to form' - do view/edit existing item?

have tried to create new item?

Yes, I click the View/Edit button on the list item. I have tried it by creating a new item. That's where I get "True" to show up and after I make the changes and remove myself from the ADMIN group and click on the view/edit item and it still shows "True."

then read once again my very first post, single line text control's default value is evaluated just and only in NEW mode and just and only on form load.

if you created new item after you removed yourself from group, you would get false.

What form controls can I use that check it every time a new item is created and viewed/edited?

calculated value control (do not forget to switch on recalculate in NEW mode).

or in general, anything what supports runtime functions.

That's exactly what I needed to know. I appreciate all of the help!

how easy it is, just to put right question

if you got resolved your issue, set the question answered.