Copy From One form matrix to another form matrix

Hello Kings

I have made a userdefined form called as InPatient , i have design separate Invoice form for it now i want to do "copy from" on Button like it is done in Sales A/R and draw form document wizard so that my Invoice form Matrix is populated with data from Inpatient form

SAme as Sales A/R "copy from " sales Order for User defined form

Plz suggest