If you mean editing more than one program at a time, the only way is to use the LOAD option in QuickBasic (not qbasic) but that kinda joins the programs together rather than keeping them separate. so the simple answer is no.
If you mean running another program then Lee answered it.
If you mean a program written in another computer language the answer is maybe. Depends. In Qbasic the source code will have to be text, and if it's not a 'basic' language program you will probably have problems trying to edit it.