Remotely Automating PLC tasks by changing tags over WLAN

We are building a small plant that packs beverage cans from a conveyor belt to a crate in responce to an order.I have been assigned a task to write an application for a Pocket PC(in Java)to enable a user to make orders remotely on a WLAN.I thought I would tackle this by writting code on the PDA that will insert a record like "insert into Ordertable values('numberofcocacolas','numberofpepsis')".A script in wincc would then read the entered record and update the PLC(s7-200) tags.Is this the best way?
Is it possible to directly reach the tags and change them over the WLAN?
Is it allowable for me to build my own table in SQL Server(Wincc) or this only for system purposes?How do I write a VB or C script with SQL statements?

Thank you