Google Docs - access spreadsheet, save locally, compare to previous

I need a simple PHP script which provides access to a password-protected google docs spreadsheet. The username/password/sheetname can be entered in the code, no need for a frontend form (unless google docs needs it). The spreadsheet should be downloaded, and filtered (removing all except 4 specified fields), then saved. It should then be compared to the previously downloaded one, and any changes made to a 'net changes' csv, which is then saved. Ie. 3 docs are saved locally: - current spreadsheet from google docs, filtered (as csv) - previous spreadsheet from google docs, filtered (as csv) - net changes spreadsheet, filtered (as csv) Net changes sheet based on SKUs (ID#s). Ie. if there is a new SKU, all data for that SKU is added to the net:new csv A previously saved SKU, maybe one field has changed. eg. Stock-quantity was 10, is now 8. so the 'net' value is -2. Net changes are 'sticky'- ie., next run, if the Stock-quantity is the same for that SKU (8), then the net csv still shows '-2'. If the Stock-quantity has changed for that SKU to eg. 9, then the net changes to -1. For text changes, the most recent value overwrites any previous value in the net csv. Eg. run 1, previous value of 'Shelf' = 'Top'. New value = 'Bottom'. Net csv -> 'Bottom' run 2, value changes to 'Shelf 2'; Net csv -> 'Shelf 2' There is another script which will clean the net values. To differentiate between 'sticky'/'non-sticky' will probably be easiest as a setting per field in the code (in case one of the 'text' values is numerical (eg. if shelf is put in as '1' then it shouldn't be subtracted from a previous '3' value). Make sense?! I can be reached at skype: jetfri if you have any questions Possible extra work doing the net-clean stuff after. ## Deliverables 1) All deliverables will be considered "work made for hire" under U.S. Copyright law. Employer will receive exclusive and complete copyrights to all work purchased. (No GPL, GNU, 3rd party components, etc. unless all copyright ramifications are explained AND AGREED TO by the employer on the site per the worker's Worker Legal Agreement). 2) Complete and fully-functional working program(s) in executable form as well as complete source code of all work done. 3) Deliverables must be in ready-to-run condition, as follows (depending on the nature of the deliverables): a) For web sites or other server-side deliverables intended to only ever exist in one place in the Employer's environment--Deliverables must be installed by the Worker in ready-to-run condition in the Employer's environment. b) For all others including desktop software or software the employer intends to distribute: A software installation package that will install the software in ready-to-run condition on the platform(s) specified in this project. ## Platform To work on any modern browser. PHP is v5, running shared LAMP server (hsphere)