Is it possible to force github to use the version of a workflow file on the current branch, i.e. in the currently active PR, instead of the previously checked in version in main?

After the initial commit of the workflow to the main branch, github actions is aware that the workflow even exists. But after that, I would like each PR to be judged according to its contents, including any updated workflows… not according to the old workflow in main.

How to do this? Thx.