Thanks all for your contributions.
I tried the code...
iif(nCounter<=alen(yourarray,1),YourArray(nCounter,1),"")
...but the report didn't stop printing, presumably because the iif statement ensures something is always printing, either the array element or a "". Experimenting with the 'Print When' feature brought no joy.
Because the original report prints correctly, I just wonder if its possible to add an error handler inside the report which can trap the 'subscript out of bounds' message and simply not display it??