I'm not sure where you want to create the button.
I presume it's on a form in your database.
First create a macro containing the following:
Runapp- with the filepath set to:
"C:\Program Files\Microsoft Office\Office\Access.exe' 'C:\My Documents\DB.mdb"
where *'C:\My Documents\DB.mdb* refers to the location of your database.Save the Macro as OpenMyDB
Then create a command button on the form that runs macro "OpenMyDB"
Let me know if it works or if you're looking to do something else
Ta
Theo