Initiate call to a SIP phone


I am running a * on my Fritzbox, connect to SIP phones via ethernet.
I was looking for a simple program where I could copy&paste a number (on my vista) and the phone next to me dail it automatically - solutions seems only to be commercial and for outlook - i only run vista w/o outlook. Anyway, do you know either such a easy tool or could you help me to give some hints, how the interface is working - so I would develop that software for my own.

I guess there is a kind of HTTP Interface to asterisk where I could sent a GET reqeust to let asterisk resp. the voip phone dail a certain no.

Thanks a lot