ilmcuts: i've just found that:
*Script Exec !IfEval ("$TasksDirection$" = "up") |Execute [!VarSet tmp %{tasksiconwidth}][!VarSet tasksiconwidth %{tasksiconheight}][!VarSet tasksiconheight %{tmp}]
use to popup an "error parameter missing"
i've tried:
*Script Exec !IfEval ("$TasksDirection$" = "up") |Execute [!VarSet tmp %{tasksiconwidth}][!VarSet tasksiconwidth %{tasksiconheight}][!Exec !VarSet tasksiconheight %{tmp}]
without success,
but:
*Script Exec !VarSet tmp %{tasksiconwidth}
*Script Exec !IfEval ("$TasksDirection$" = "up") |Execute [!VarSet tasksiconwidth %{tasksiconheight}][!VarSet tasksiconheight %{tmp}]
works !

i guess it's due to !Execute