Client Database

The firm I work for currently has an Microsoft Excel quoting workbook with multiple linked spreadsheets. The workbook resides on a central server and is downloaded and modified to allow quotes to be generated. Within the workbook there is a site data entry spreadsheet which contains cells that are manually infilled by sales staff with client and site details. Currently there is a dropdown that can be used to select existing clients that are held on the client details spreadsheet within the same workbook. If an existing client is selected, the clients details are autofilled in the lower cells by VLOOKUP functionality. I would like to be able to develop a system whereby the site details spreadsheet draws on client details saved in a remote linked master workbook/worksheet file. If the dropdown (or search method) shows the client is new, the details can be manually entered into the site data spreadsheet and then an option offered to save this data and update the remote client details worksheet. I have other Excel projects to undertake but this is the first.