I wrote a version of the M6Start.m1s macro for a manual tool change.
If the M00 code is used within M6Start.m1s then it stops the operation of M6Start.m1s and bypasses M6End.m1s. Control passes to the following command in the G-Code file.

For example: the following code fragment would fail after the M00 command:

  Message "Release old tool(" & oldtool & "). Insert tool" & tool
  CODE "M00"           ' Stop
 
  CODE "G0 G54 Z0"      ' Move to zero ready to lock the tool
  While IsMoving()      
    Sleep 100
  Wend

This work around is the best I can do:

  Message "Release old tool(" & oldtool & "). Insert tool" & tool
  MsgBox("New Tool Inserted?")      ' wait for operator

  CODE "G0 G54 Z0"      ' Move to zero ready to lock the tool
  While IsMoving()      
    Sleep 100
  Wend

Note: the Message precedes the MsgBox command because MsgBox can only accept a simple text argument.

Questions:
A   Is there a better way of doing this?
B   Is it possible to fix M00 so it can be used in this context?
C   Would it be possible to extend MsgBox so it can take multiple arguments including a title for the box?
D   Is there a way to use a more complex text string with MsgBox?