Not sure if I understand.
You want a file called "Form" and in this file you want each vendors workbook.
The workbooks will be named with the "Vendors" name. Now each vendor will have more than 1 Invoice. If thats the case you fill in data for 1 invoice. What do want to do with the other invoices for that vendor.
I'm off to bed. But look at this tomorrow.
Let me know if my assumption is correct and add anymore ino that you can.

I was referring to the workbook I attached called "Form" in my original post.

I want each vendor to have their own file. Once the macro runs, I should see the file "Form" for each vendor with Sheet1 and Sheet2 populated.

It should populate as so...
"Test Data1" column A should populate "Form" sheet1, cell D8

"Test Data1" column B should populate "Form" sheet1, cell D12

"Test Data1" column C should populate "Form" sheet2, cell B6

"Test Data1" column D should populate "Form" sheet2, cell C6

"Test Data1" column E should populate "Form" sheet2 cell D6

Sorry for any confusion.