Populate Values in Multiple List Boxes based on Multiple Criterias

All,

I am completely stuck and don't know where to even begin. I've attached my workbook to this post.

Background of Workbook:
InvoicingForm Worksheet is used to pay off invoices.
InvoiceDatabase stores Invoice Information.
PaymentDatabase stores payment information.

Two buttons:
Add Invoice - Userform to enter invoices.
Outstanding Invoices - Userform to show outstanding invoices.

FYI - Need invoices before payments can be made. "Add Invoice" button is used to add the invoices. Then use the InvoicingForm to make payments to the outstanding invoices.

Issue is the Oustanding Invoices Userform:
I am trying to populate the first listbox with all of the oustanding "Customer Name" values based on the Company Name field (companyNameInput) from the Outstanding Invoices userform. To determine the oustanding invoices, it would look in the InvoiceDatabase and the PaymentDatabase to determine which invoices have balances. Then, after clicking a Customer Name from the list box, populate only the outstanding Invoice Numbers which are dependent on the Customer Name/Company Name. After that, populate the outstanding categories which are dependent on the Invoice Numbers/Customer Name/Company Name. Can anyone please help with this request?

Thank you in advance!

J