How to set threshould from query variable?

Hi all.
Pls tell me, I just can’t understand and find how to set the threshold values from a user variable of the query type. The manual says that “enter the variable name in the threshold field, exapmle {$value}”, but this field only accepts numbers.
I use Grafana 10.4.0

Thx for help.

Hi @vovabelov78 welcome to forum

What are you attempting to do with these thresholds?

I have a disk 10Gb with tempdb data files, but their size is special for each database server. Therefore threshold value depends on each value individually and is actually calculated. I want to calculate this value and set it as a threshold.