Logical condition in Screen flow Logic

Hi

While enhancing a Screen flow logic, I need to control the execution of a particular module.

i.e.

If flag = 'X'

<<< Module execute. >>

else

<< skip module. >>>

endif.

But neither I can put if-else in flow logic, nor I can set/check any flag inside the module (can't put any code there)

Please provide a solution.