I have a spreadsheet containing orders per month for 2004, 2005 and 2006,
i.e. to date it has 25 values in it (up to and including Jan 06).

I want to create a graph that displays the last 12 months data
automatically, i.e. when the sales manager inputs feb 06 data, the graph then
changes from displaying jan05-jan06 to feb05-feb06 data.

I realise that my issue probably isn't the graph, but creating a table that
recognises when a cell changes from blank (or zero if necessary), then the
twelve month data has moved down a cell.

Hope this makes sense - please help!