Make it fewer pages! There is way to much separation of things that don't need to be separated.
1. Let me put in all locations, arrival/departure dates, lodging costs and per-diem on a single page. Give me a check box if one location has changing costs or special requirements and then i can revert to the current PITA way of doing it.
ie: Location 1: Date Arrived: XX/XX/XX Date Departed: XX/XX/XX Daily lodging: $XX.xx Daily Per-diem: $XX.xx Special circumstances ? Y/N
Location 2: ....
2. Put mileage / non-mileage expenses on the same page. Hell, put em in the same drop-down.
3, Stop telling me arrival/departure dates aren't authorized / stop isn't authorized / etc. If I arrived on a certain date, that's the date I arrived on. Obviously it was either authorized or required. Let it be!
4. Make it look like the paper voucher. The paper voucher didn't require help filling out. The digital voucher should be even easier. If it's not, it needs to be re-done.
5. Once the new system is designed find the lowest common denominator and have them run through the entire process. If they can't do it without help go back to the drawing board. If the program freezes/ crashes/ etc fix it before publishing. And do it on an old gov't computer running vista. Don't use the brand new Win 7 (or 8 or 9 by then) system.