Switching Two Workbooks And Transferring Data With Variables

I have create a nice invoice with macros to random insert pages and summations etc. Works fine, but to complete it I want to go one step further and there ìt got out of hand.
I want to create the following, but I can not get al this combined in two Macros.

Basis: Workbook 1 = Invoice, Workbook 2 = Invoicelist
Required actions Macro1:
1. Starting point is that Workbook “Invoice” is open.
2. The user activates Macro1.
3. Check if Workbook “Invoicelist” is active.
4A. If YES then continue,
4B. If NOT then reply with some sort of Alertbox “Invoicelist not active! Click OK to open (needs to open Workbook “Invoicelist” or Cancel to stop (needs to stop Macro).
5. Workbook 2 “Invoicelist” is now open.
6. Find the last invoicenumber in the list. Add “1” and put the new number to the list (to prevent using double numbers). Then I want to take this number to the “Invoice’ workbook, but that can be done by copy and paste.

Now I get really stuck because I want to use variables instead of multiple copy paste actions.

Required actions Macro2:
7. We are in Workbook “Invoice”, the user activates Macro2.
8. Same check if Workbook “Invoicelist” is active as in Macro1.
Several data from “Invoice” has te be transfered to “Invoicelist”. And to be safe, this does not have to be the last cell if the user “forgot” to store date for a previous invoice!
9. Store data from sevaral cells in variables, including invoicenumber!
10. Find invoicenumber in “Invoicelist”.
11. Paste data from variables into fields on same row as correct invoicenumber.
12. Save Workbook “Invoicelist”.
13. Go back to Workbook “Invoice”.

The two problems I cannot fix is checking if Workbook is Active and store and use cell values with variables.