Hi Mahmud
Unfortunately there is no way to immediately ASSIGN a value to an TEI Attribute while you are updating a program stage. You would need to again open the registration form with the TEI Attributes.
This is by design: here is an explanation from Markus
Of course there may be workarounds with custom scripts etc to update the TEI attribute via a PUT request, depending on the use case, but there is no built-in solution. Perhaps you could consider a warning box in the program stage to ask the user to update the TEI attribute. There is also the option to ASSIGN the TEI attribute value to a data element when the program rule is executed.