Macro with parameter

Hello
I would like to make macro with using a model parameter.
I need macro to save drawing to dxf format. The name of dxf file has to be same as name of model.
The name of model is one of parameter.
I don´t know how automaticly use this parameter to create macro.
(I don´t want to write the name of file after start the macro)

Thank you for the advice