Hi,
I understand your requirement and YES it is possible. What you are looking for, is a macro written in VBA for Microsoft Word. So once you copied that macro in your MS Word (to be done once) it will be running in the background. Every time you will open the word file and type anything it will detect the word is matched with your databank and it will replace the word with the replacement.
We are a group of expert developers who can deliver this solution. However there are a few things we would need to clarify from your requirements before we proceed.
1- Do you need to do this on multiple computers?
2- How is the databank stored in the PC, can you give the copy of the file?
Send through your data file and a sample word file and I can arrange a demo solution (with no obligation).