procedure cad_open(fpath:string);
 var
    obj_Acad ,obj_Doc: OleVariant;
begin
 try
   obj_Acad:=GetActiveOleObject('AutoCAD.Application');
 except
   on EOleSysError do
   obj_Acad:=CreateOleObject('AutoCAD.Application');
 end;
  obj_Acad.Visible:=True;
  obj_Doc:=obj_Acad.ActiveDocument;
  obj_Acad.Documents.Open(fpath,False,'');
end;打开CAD文件时提示"无效的参数数目",请各位大侠指点!