get latitude longitude for multiple data for Google Map

so i have a complete list of 4000 houses, with their complete details in excel format, which, given their postal codes, i have to look for their locations and insert the latitudes and longitudes on Google Earth (their approximate values, based on my common sense, visually speaking ifever i come across an empty plot of land) back in the excel sheet. after that i shall then convert all this info into an xml sheet which i shall then deliver to my programmer for inserting in his flash application

thing is i managed to create and generate the xml sheet from the excel sheet, which was not easy, since there were loads of special characters (everything was in french, you can imagine the apostrophes and the special characters) and hard to convert to csv for importing via phpmyadmin.. but i did it ! a designer did programming finally !

however i still have to insert the longitudes and latitudes for 4000 houses on my sheet
im already starting it, cos my boss wants to see results :( for 4000 items, with all the searching and all the xml (nyehehe, the xml saved me time ^^), it will take me around 10000minutes which rounds up to approx 200hours, a month approx

is there any automated way or some way that can facilitate this hideous task ?

thanks to revert

ps: for those wanting to know how i managed the xls xml conversion with the special characters and the french accents taking care not to mess up the utf formats etc... email me :)

in reference to: Searching with latitude and longitude coordinates - Maps Help (view on Google Sidewiki)