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- Add an attribute to Bill Running totals with Name BillsRunningTotal
- Use the cache() function to calculate a running total for the amount billed so far on each account. Remember to use, as a key in the cache function, a different key from that used in the expression to calculate the number of bills so far (if you use the same key for both, the values will clash). You can use the ACCOUNT_NUM field again, but this time concatenated with a fixed plain text string, e.g. _out.ACCOUNT_NUM+"-RunTotal"
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