When your first ressource assign is done, you can set a custom variable with the box "variable assign".
Here is an example of an entry : session.logon.last.your_custom_variable_name = expr { "flagged" }
Next thing to do is to create a macro beginning with an empty box to create your condition like that :
Into the branch rules tab, you can set your condition into the advanced part :
mcget {session.logon.last.last.your_custom_variable_name} == "flagged"
You will have to branches, and on the fallback one you can create your resource assign box.
I'll try to make a VPE screenshot later to make it easier to understand.