so you can't replace

%CALC{"$SET(show_from_number, $MIN($TIMEADD($TIME($FORMATTIME($TIME(), $year-$month-1)),-1,month), $TIMEADD($TIME($FORMATTIME($TIME(%URLPARAM{showfrom}%), $year-$month-15)), 3, month)))"}%

with

%CALC{"$SET(
    show_from_number, 
    $MIN(
        $TIMEADD(
          $TIME(
            $FORMATTIME($TIME(), $year-$month-1)),
            -1,month
        ), 
        $TIMEADD(
          $TIME(
            $FORMATTIME($TIME(%URLPARAM{showfrom}%), 
            $year-$month-15)
          )
        , 3, month)
     )
)"}%

or something that would work easier for the writer (i don't know a good style, but atm, we prevent one

-- SvenDowideit - 20 Jan 2009