How to add a constant variable in a expression

Hi community,

I have created this constant variable in the Grafana(v8.1.1) dashboard settings:

And now, I want to divide this constant variable with my query in the expression field but am receiving this error “expression request error”

A,B,C…,H are all time series queries which I am adding up and want to divide it by the constant variable “AllPBWs”. The panel I am using here is “Stat”.

PS: I know that I can directly divide the expression with the constant number but I want to refrain myself in doing so because I want to use this constant variable in various other panels and would like to have a single location (dashboard settings) to make any changes to the constant variable in case I would like to update it in future.

Can someone please help me with it?