Route delivery

I run a newspaper and magazine distribution company and keep all our customers supplies, returns and sales in an Access database. At present all forecasting of future deliveries is done through the access database. However all returns are captured manually from sheets that are carried by the delivery team. The delivery team also manually create a cash sale for all sold copies at each shop. I am looking for a programme that I can run on a PDA (or other handheld device if advised) that will load the needed data from access and then according to specified parameters charge for any sold copies as well as capture returns. Then when the delivery team returns to the office, the data can be merged back into the access database as well as run a few reports that will show what returns were collected on the route and also what sales were charged. Obviously this is vague but I hope the basics have been covered. I would also like the source code for the programme to be open so that if I need changes in the future anyone can do them. I would aso like some sort of support (3 months) to make any changes required if we problems occur when being used by the delivery teams.I would also be willing to offer accomodation along the North coast of South Africa in St Lucia as full/part payment (A monetary value of this would be agreed so that this website still receives their commission)