Here are some of the steps. Maybe others can fill in other pieces. I'm not sure how much you know so I will go step by step. My apologies if you know much of this.
1. Open the word document where the mail merge is created
2. On the Tools menu, Select Tools, Macro, Record Macro
3. Name it, make notes or whatever
4. Make sure you save it in the Normal file so that it will be retained for you
5. Go through the mail merge steps
6. When finished click Tools, Macro, Stop Recording
7. Click Tools, Macro, Macros and then select the macro you just crated - Click edit to view the VBA code it created
8. Open access and create a new module
9. Click on the Tools menu and select References
10. Scroll down to the Microsoft portion and click on the one named Microsoft Word x.x Object Library
11. This allows you to control Word from Access
12. Add the following lines at the beginning of your sub or function - this code creates a word app for you to control
Dim objWordApp As Word.Application
Set objWordApp = CreateObject("YourWordFileNameAndPath"
13. Add the following line before the First piece of code that the Word macro created for you - this tells Access to use the Word app object you created when it processes the Word commands below
With objWordApp
14. Add the following line after the Last piece of code that the Word macro created for you - like If/End If pairs
End With
Sorry, I have to leave for work. Hopefully this will ge you started anyway. Good Luck!