Make Solder Mask an active layer and draw copper or closed polygon copper on that layer and it will be your void in solder mask.
Thanks but I need to remove the open on solder mask; what I need is to have solder on copper track; now in this component over the track the solder is open and I don't like this
I am not sure what exactly you are trying to achieve. If you have a component resembling an antenna, you can build in solder mask opening of the antenna into Decal using same technique I have outlined earlier.
If you don't need solder mask opening over antenna, make sure there is no copper on solder mask layer is in Decal or in layout.