Increment a named variable in Excel

Question

I'm trying to increment a named variable in Excel, similar to the VBA command 'x = x + 1'. I'm using the syntax:

=LET(Test1,Test1,Test1+1)

Test1 is my named variable which I elsewhere set to 1. The above formula returns 2 (as expected) but that assignment doesn't seem to persist. Subsequent references to Test1 still return 1.

Is there a way to permanently set Test1 = Test1 + 1?

Thanks in advance for your help.