Connecting Voice Modem & Sound Card

I have an Intel EPS536 V92 Data/Fax/Voice modem with speaker phone capabilities and I wish to use a headset and microphone with it for dialing and talking instead of using the handset.
I sometimes make more than 200 phone calls a day useing ACT! V6.0 as my contact management program.
I also would like to be able to play a WAV file through the sound card to the prospective customer over the modem while on the call.
I have a CMedia 8738 sound card.
I am using XP Pro.
I have found software that will record the call, but nothing that will do what I describe above.
Anybody got any ideas?
Can I patch cord the microphone in/out on the sound card to the in/out on the modem?
I've tried everything I can think of.