To make it easier for people to enter data, you can create drop down lists on an Excel worksheet.
In the screen shot shown below, the original list is in the workbook at the left. The drop downs are in a different workbook, on the right.
There Is a Catch
My preference would be to keep the lists and drop downs in the same workbook, but if you need to have them in separate files, this technique will allow you to do that.
There’s one catch though, when using this data validation technique. The source workbook, which contains the original list, must also be open, when you are using the drop down lists.
So, it’s not a perfect solution, but it’s fairly easy to implement, as long as you remember to open the other workbook too.
Excel 2010 Instructions
I’ve just uploaded a video with instructions for this technique in Excel 2010, so you can see the steps for creating the named ranges and data validation drop down lists.
The written instructions for Excel 2007 and Excel 2010 are in this blog post: Data Validation List From Different Workbook
You can also watch the video on YouTube: Excel Drop Downs From List in Different Workbook