Error on Changing BI Publisher default display 'NaN' to 'NA'

Hi There,

I am working on BI Publisher template(rtf),  some of the calculation result showing 'NaN'  when divisor = 0 as BIP default displaying, I am trying to change 'NaN' to 'NA' as customer requested. There is no issue with detail line calculation as I use the following formula:

<?xdofx:  (if APPS_TOT_PY IS NULL then 'NA' else ((if APPS_TOT_CY IS NULL THEN 0 ELSE APPS_TOT_CY END IF) div (APPS_TOT_PY))   -1)?>

("total number of Current Year Applications" divided by "total number of Previous Year Applications" - 1) to get the change in %  (Current Year Applications vs Previous Year Applications)