Using TREND With Updating Data

Hi Folks,

Looking to predict future warranty claims based on previous data. Actual data is updated into spreadsheet weekly, and looking to extrapolate potential future claims from the actual data.

Seem to be having a case of Excel writers block on how to go about it..... I was thinking of the TREND function, possibly with dynamic ranges, but am not getting good results. Since there are dozens of items - and dozens more production lots - and needing to "scale" this adds to the difficulty since data varies depending on the start and end of data in the range, and new data will be coming in weekly.

Here's an example of data I'm trying to get a future "trend" or forecast on:

http://www.filedropper.com/warrclaim

The cells highlighted in yellow are the future data I'm looking to "predict" data for.

This has really got me stuck so even just pointing me in the right direction if I'm way off here would be greatly appreciated.

Regards,

Ray Jr.