[rules-users] Can I use not and from in same condition?

Hi, I get an error with the following rule that appears only when I use the not keyword. If I remove the not keyword, it seems ok: rule "WCDMA->GSM Bidirectional Relations Evaluation Rule - Version 4" salience 10 dialect "java" when $extgsmcell : ExternalGsmCell() $utrancell : UtranCell() from $extgsmcell.getIncomingUtranCells($extgsmcell.fdn) $extutrancell : ExternalUtranCell ( rncid==$utrancell.rncid, cellid==$utrancell.cellid ) not GsmCell( lac==$extgsmcell.lac, cellid==$extgsmcell.cellid) from $extutrancell.getIncomingGsmCells($extutrancell.fdn) then System.out.println("Version 3: Missing Cell Relation from " + $utrancell.getFdn() + " to " + $extgsmcell.getFdn()); End Any suggestions? Thanks, Ryan.