Create a chart that takes a 'snapshot' of changing data

[TS057]

Like the title says...

Basically I have a spreadsheet that is updated bi-weekly or monthly. It contains a more-or-less fixed number of rows. The status of the item that each row represents changes somewhat frequently. I want to create a chart that documents this status on a bi-weekly or monthly basis. I want to be able to add new columns to the chart (for each week/month) without having to create a new column in my worksheet and without loosing the data from the previous week/month. Like I said I'd somehow like the chart to represent a 'snapshot' of the status summary and be able to add more 'snapshots' to the same chart without losing the original chart information. I hope this makes sense..