Automatic invoice charges based on date selection

Hi guys,

I'm having a pig of a time trying to do the above, so I thought I'd bounce my issue off you and ask for some feedback.

At the moment I have an invoice worksheet, and with it, a secondary sheet listing periodic charges (name, charge, month the charge becomes active (mmm format)).

I want to make the invoice self-completing based on date selected.

Any suggestions/advice on how you would go about the above? I'm sure my current formulae are kinda overcomplicating the issue, and that there is a much simpler, more elegant way of doing things (not to mention one that works)!

Thanks.