Here are the changes you need to MSGED to make it compile with MSC 6.0 for
OS/2 with Squish support...

Index: makefile.mso
===================================================================
RCS file: e:\cvs\msged\src\makefile.mso,v
retrieving revision 1.4
diff -c -r1.4 makefile.mso
*** makefile.mso	1996/07/24 00:10:46	1.4
--- makefile.mso	1996/08/17 13:15:44
***************
*** 5,11 ****
  #COPTS=
  
  .c.obj:
!   cl $(COPTS) -c -DMSC -DOS2 -DOS216 -UMSDOS -I$(MSGDIR) $<
  
  objs=areas.obj    \
       bmg.obj      \
--- 5,11 ----
  #COPTS=
  
  .c.obj:
!   cl $(COPTS) -c -DUSE_MSGAPI -DMSC -DOS2 -DOS216 -UMSDOS -I$(MSGDIR) $<
  
  objs=areas.obj    \
       bmg.obj      \
***************
*** 29,34 ****
--- 29,35 ----
       menu.obj     \
       misc.obj     \
       mnu.obj      \
+      msg.obj      \
       msged.obj    \
       mxbt.obj     \
       normalc.obj  \
***************
*** 49,52 ****
       wrap.obj
  
  msgedo.exe: $(objs)
!   cl $(COPTS) $(objs) -Femsgedo.exe -F 2000
--- 50,53 ----
       wrap.obj
  
  msgedo.exe: $(objs)
!   cl $(COPTS) $(objs) -Femsgedo.exe -F 2000 $(MSGDIR)\msgapimo.lib
@EOT:

---