;Returns a zero if the passed string contains non-numeric characters,
;a one otherwise
func IsNum : integer
   param string sNum
   integer iLen, iCount, iVal

   strlen sNum iLen
   for iCount = 0 upto iLen-1
      strgetc sNum iCount iVal
      if ((iVal < 48) || (iVal > 57))
         return 0
      endif
   endfor
   return 1
endfunc