As I understand, you want receive calls from FXO of AX and route to D3000. There are many ways that this can be done and first we would need to determine which of the ways you want to do this. You could use a calling card solution, if you have a radius which provides security about who can call where, or if you are not concerned, then there is just a simple 2nd dialtone with no security. Depending on the setup of your D3000 there could be other ways, but we would need to discuss them.
I suggest you contact me directly at firstname.lastname@example.org and we can discuss the details. I am also, many times, online on MS Messenger so we could chat as well.