Changing a cell reference

Hi

Please can you have a look at my sample file
I have three sheets - Actual( which has actual figures from Jan - Dec), Budget ( figures from Jan - Dec) and a Summary sheet ( which is just the summary for the current month, say July and compares the budget VS Actual)

Every month i need to change the summary sheet to the next months set of figures, say Augusts etc etc.

Currently i've been using find and replace, and changed the formula to the correct months column - but its a rather large spreadsheet( its a management accounts pack and has many many more sheets that link up - like lasts years comparison etc etc)

Is there any easy way of linking ( without VBA) or anything complex, so that each month i can change my data easily?

Thanks a mill