"group by attributes with macro"

Hello


I'm trying to make a proccess that group attributes, but i would like to make this with a macro. In the "Select Attributes: group by attributes windows a put %{mimacro} in the "select attributes " textbox and  then I add this item. Sadly when I run the proccess I realize that my operator has been changed. The name now is mimacro, without %{}, and obviously I get a undesired result. Could anybody give any advice?