How can I create a drill down

Hi

I am preparing a budget template that has a column for cost code and a column for amount. Users are being asked to fill in relevent amounts against the cost code.
I would like to add the ability for the user to double click on the cell containing the amount and have this double click event open a second sheet that allows the user to detail the various components that make up the budget figure. This drill down sheet would then be saved as part of the work book and could be reviewed by any user of the budget to drill down into the detail of the budget. Make sense?
Any thoughts anyone?

Thanks