how to automatically record serial no. on next available line

I have a spreadsheet that contains two sheets. On the first sheet is an invoice template. On the second sheet is a list that contains data on all previously prepared invoices. Is there any way that I could enter data into the invoice, and then run a macro that would (1) take data from the invoice, such as serial or invoice numbers, and enter it on the next available line in my invoice list, and (2) clear the invoice template? Any help would be appreciated very much! Thanks,

kevin