Have you tried ThisDrawing.SendCommand Chr(27) & Chr(27) & Chr(27)
thinking more on it, I think I had to do it as two subs because I couldn't start the plot while I was in begin command still.
Begin command
if flag is false
cancel
flag = true
else
flag = false
end if
end sub
end command
if flag then
spell check
plot
end if
end sub