Deals - Forumula -working out the weeks between 2 dates

Deals - Forumula -working out the weeks between 2 dates

Hello,
I have managed to create the formula for how many days there are between 2 dates (invoicing):

Datecomp(${Deals.Invoice 3 - Date},${Deals.Invoice 1 - Date})/1440

However I can't figure out how to do it for the number of weeks...

Can anyone help?

thanks in advance