Creating a table out of Strings + Saving as an XML File

Hi, for my collage I've made an small App, that reads out Data of an vehicle over the OBD 2 Port (Such as speed, RPM and so on) Now I write the Values in an txt an send them to an Server. But this isn't very useful because You cant find what You need. Now I want not to write them into an txt but into an xml as an table First of all there should be the Date and for this date with the specific time the speed RPM an so on. This File should be created once and if its allready created the app should put the new values with the new date and time and the end of the file! Thanks klist