Using message box to monitor a repeat loop

[David Epstein]

When running a repeat loop for a large dataset, I want to be able to monitor progress, so 

repeat for each line k in myData
   put k ## into message box to see what’s happening
   ## do the actual work…

I believe this has worked in the past, but in a current project the “put k” only has effect when I am debugging, not when the script is running normally.  I have not locked screen or messages.

Any ideas why this doesn’t work?

Best wishes,
David Epstein