Variable Substitution in Postgis Query

[Maurizio Esposito]

Hi list,
I'm in trouble with this:
In Mapserver CGI I use a var &ruolo=XXX set by form - all OK
In mapfile in a Postgis layer I need to use this FILTER clause
FILTER "pk_id NOT IN (SELECT feat_id FROM features WHERE feature.type='%
ruolo%')"
but substitution doesn't work.
I've tryed all combinations of single and double quote, with or without,
but no results at all.
Inserting a value , say 'foo' , makes the filter work fine.
Any help ??

Regards

Maurizio