... then I answer my own question:

I used ent_cloneskin to make a copy of the bitmap used by my entities,
and since there is bug in 7.66 engine I used vec_to_uv to correct the bug.

then I created a new black bitmap, copy the content of the original bitmap of my entity into the new bitmap with bmap_blit.

then I used ent_setskin to assign the new bitmap to the box entity.

that solved the problem.
thanks to all who tried to help and sorry for my bad english.
Regards.