opener.document is undefined?

Good morning.

I have this in form b:

 function ue_aceptar_reportedesde()
{
    opener.document.formulario.cmbcodtipsol2.value="";
    opener.document.formulario.cmbcodtipsol2.disabled=true;
    close();
}

The cmbcodtipsol2 is the id of a select of another form A. There is a way to tell it that the cmbcodtipsol2 belongs to the form a since that is why I get the undefined error.

I do not know if I can explain, sorry if I can not do it, I'm new in this world.

Thanks