Re: calculation of DSO (day sales outstanding) per month
The best way to get help with these situations is to attach a QVW file with your data model and some data that reflects what it is you are trying to solve, does not have to be actual, can be sample, but the data model should reflect your total model to ensure you get good responses. Trying to provide assistance with what you provided is rather dicey which is likely why nobody has responded at this point. If you have not figured things out, the only place I can point you that will likely be of some help is the Design Blog area, there are hundreds of how-to posts from our experts in this area, so you may be able to find something there to assist you in developing your expressions, but I suspect you may need to use some Set Analysis on this one potentially and possibly use the AGGR function too.
If you can attach an example QVW with some data etc., that should be helpful in getting further responses.
To help users find verified answers, please do not forget to use the "Accept as Solution" button on any post(s) that helped you resolve your problem or question. I now work a compressed schedule, Tuesday, Wednesday and Thursday, so those will be the days I will reply to any follow-up posts.