Inserting new column, hiding oldest column, 12-month total

Hi.

Could anyone help me with the following problem:

I have a sheet with monthly cash flow calculations (inflow, outflow, net cash and cumulative cash) and a 12-month total column. At the end of each month, I want to add a column with a new month and hide the oldest one, in a way that only the most recent 12 months are visible. The 12-month total should also reflect the sum of only the latest 12 months and drop more than 12 month old figures.

How should I go about it using macros?

I would appreciate the help.