You can do the same as explained in the previous discussion.
It doesn't matter if it is a sub assembly or a part.
Edit the part in assembly, select the face you want the hole to be placed, then moce the mouse over the edge of other hole and pick the mark
what does "it dosent work" means to you , even if you have 'n' number of sub-assemblies in an assembly you are going to edit just one single part. So you can do it as mentioned in other forum