Is there a way to set a flag or create a user-controlled variable in a channel entry?

Is there a way to manipulate/create a variable in an entry? I’m using a plugin I bought but its not as robust I had wanted.

I’m supposed to use it like this:

{exp:member_categories:check category_id="1"}

//If True, shows this

{if no_results}

//If not true, shows whats in here

{/if} 

{/exp:member_categories:check}

But I want it to be able to check multiple category_id’s…That only checks one.

So I want to create a variable that sets $isitokaytoshowthis=1 if multiple category id’s are set to true.

Does EE allow something like this? I cant seem to use PHP in my wysiwyg editor to make variables, so im out of options.