List box after update coe

[rbeech23]

Hi
I'd like to populate a cell from the contents of a list box containing CompanyName once a selection is made. The list box is in Sheet1, the list is generated from CompanyName data in a column in Sheet2. In Sheet3 there is a column containing CompanyName data along with a DiscountRate and various other fields.
When the user selects from the list in Sheet1 I'd like a row next to CompanyName to display the DiscountRate from Sheet3 where the CompanyName in Sheet3 matches the selection made. I think it's some kind of vba after update code but not sure how to implement, any help appreciated, thanks

[torachan]

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[rbeech23]

Apologies for the sparse detail. I've removed sensitive data and tried attaching a file called forum.xlsm in Manage Attachments but can't tell if it's uploaded. From the attach file icon in Your Message when selected nothing happens apart from a blank line.
If it has uploaded in sheet QuoteGenerator there is a list box under 'Select customer', the company names are derived from sheet source_data, column d. In sheet order_data there are rows containing the company name and other details one of which is a discount rate if column g = Gate.
What I'd like is once a company name is selected for the discount rate to be selected. There could be multiple references of the same company so I'd like to loop through each and keep the highest discount rate value and display that in sheet QuoteGenerator in column f6.
If the file hasn't uploaded I'll try again...