Formularios modales y no modales

[[coso]]

mira, usa esta funcion,

Código Delphi [-]
function MDI_a_Modal(f : TForm) : TModalResult;
var
    mr : TModalResult;
begin   
          try   
          f.FormStyle := fsNormal;        
          f.Hide;        
          mr := f.SHowmodal;        
          f.Hide;       
          f.FormStyle := fsMDIChild;
          except
          mr := mrCancel;
          end;
          MDI_a_Modal := mr;
end;