How to get info from one sheet to another automatically in a workbook without vlookup

Good morning,
I have posted this before but maybe I didn't work it right or something. This is due wednesday and I'm very stuck. I'm attaching my workbook, what I am trying to do is create an invoice tracker for this company. On the Invoice Main tab the assistant creates an invoice which then the technician can fill out on the Invoice tab, the drop downs take them to their invoice and then they fill in what they sold. How the technician gets paid is based on the hours sold, so I included that. Now where I am stuck is, I can't figure out how to get those hours sold from the Invoice tab to pull over automatically to the Hours Sold tab. They want it to calculate per invoice and also calculate totals.
I was thinking a simple vlookup to pull over but based on what? the sheets have nothing in common except the invoice number but that is in the drop downs of the Invoice tab not on the rows themselves.
It's ok if I need to redo something to make it work or even revamp the entire workbook, I'm open to any and all suggestions. This is time sensitive so if you can help, please do! I'd greatly appreciate it, thanks!