doh, my script didn't work as it didn't switch anything at all :/
well, sorry hen, has been way too late yesterday ;)

should have been:
*script exec !ifeval ("%{labelpopuphidden}" = "true") {!execute [!Labelpopupshow][!varset labelpopuphidden false]} else {!execute [!Labelpopuphide][!varset labelpopuphidden false]}