Looking for Help with Conditional, Dependent Drop Down List

Hello,

I am trying to create a conditional drop down list that is dependent on the number of variables available in a supporting table. My data has vendors in it that have associated general ledger accounts. If a vendor only has one associated account, I just want to return that account. If a vendor has multiple associated accounts, I want to return a drop down list with the applicable accounts so a choice can be made.

Example of the source data is:

VendorID AcctDesc1 AcctDesc2 Acct Desc3 Acct Desc 4
Vendor 1 Office Expense Supplies
Vendor 2 Meals
Vendor 3 Software Equipment Licenses

So if cell A1 has Vendor 2, I want cell B2 to populate "Meals." But if cell A1 has Vendor 1, I want a drop down list that shows the options for "Office Expense" and "Supplies." This list of vendors could grow pretty long so I am trying to avoid having a named range for each row of vendor master data.

I have attached a sample file. I am truly grateful for any assistance.

Requirement is not clear, please remove unwanted data and give answer in excel manually.
Conditional drop down list is possible.

Regards,
Suhas