Portal sum - Field or Script?
I have a portal on a layout that is part of an expenses database. In the portal there is a "Payment Type" field. This field has a drop down menu to select - VISA (V), MasterCard (MC), Cash (C), Travelers Checks (TC), etc. etc.
I also have a Summary layout that displays fields representing a variety of sum totals for different expense values both dollars and just numbers (such as 'miles per gallon' averages; etc.). However, I cannot figure out how to do the following sum(s). I want to have separate field(s) on the Summary layout that represent the running total or grand total for all "V" payment types, all "MC" payment types, etc. etc.
I can visualize -somewhat- a script to cycle through the records and find each type of payment but I do not know how to get the script to collect all of each 'payment type' and then total them and post the results to respective total fields.
I would really like a calculation field to do this but I don't think it is possible.
So, I think I might be locked into a script which raises my final question: Can a script be triggered somehow to run when I go to the "Summary" layout without having to click a button each time to run a script? If so, how would I do that????
Any input on the best way to get my goals accomplished will really be greatly appreciated.