Suppose using varible interpolation, I assign a certain category as "Cat2"

I can then display entries under that category:

<MTEntries category="$cat2">

I understand that MT4.1 would have no problem with this either:

<MTEntries category="mycategory1 AND mycategory2">
(in other words, "show all entries that are filed under mycategory1 as well as mycategory 2")


BUT I understand that MT4.1 does not allow complex expressions like this:

<MTEntries category="mycategory1 AND $cat2">

Is there a way to get around this -- perhaps using regular expressions?