Turboprop Captain reports TCAS event descending into DFW between 7000 and 5000 FT outside Class B. Two other aircraft were involved and results in multiple and varied TCAS RA's. Closest approach is to a Bonanza; co-altitude and less than 500 FT horizontally.

Narrative

I was pilot-flying to DFW. We had been handed off from DFW Center to Regional Approach while descending to 7;000 FT. ATC cleared us to fly heading of 100 degrees to join the localizer for 13R at DFW. We were approximately 40 DME out from the localizer. At that time; we noticed a traffic symbol on TCAS at 10 to 11 o'clock and several miles. We acquired the traffic visually; and I told the First Officer that it appeared 'as a speck.' We continued to monitor the traffic; when ATC reported traffic to us in that position; at 7;500 FT; a VFR Bonanza. We reported traffic in sight. ATC then cleared us to descend to 5;000 FT. While descending at 1;000 FPM; TCAS issued a; 'TRAFFIC! TRAFFIC!' advisory. I looked at the VSI/TCAS to determine location of the traffic and then looked forward to try to locate the traffic visually. I saw an amber traffic symbol very close to our aircraft symbol; 200 FT below us; and climbing. TCAS issued 'MONITOR VERTICAL SPEED.' I immediately disconnected the autopilot; and looked at the VSI to determine the recommended RA vertical speed. A red arc appeared; and covered all descending options; so I leveled the aircraft at that altitude (I do not know the altitude we leveled at--it was between 7;000 and 5;000 FT). I still did not have the aircraft in sight. ATC then issued an alert; 'Traffic at 1 to 2 o'clock; two miles; a VFR Cessna.' During that transmission; TCAS issued a 'CLIMB! CLIMB!' command. I advanced the power levers; and immediately pitched up; then looked at the VSI to determine VS required. It was commanding nearly 2;000 FPM. The First Officer reported to ATC that we were responding to an RA on the Cessna. TCAS then issued a second; 'MONITOR VERTICAL SPEED' command with red arcs from approximately +300 FPM and up; as well as from 0 to -2500 FPM descent. I was pitching the aircraft down to comply with the RA; when TCAS issued 'INCREASE CLIMB! CLIMB! CROSSING CLIMB!' and the VS required indicated over 2;000 FPM. I immediately changed the power management selector to the max continuous torque position; and increased the pitch to attain the required vertical speed. The First Officer visually acquired the Cessna below us; and turned toward me to advise me; when he saw the Bonanza in our 11 o'clock position. He announced; 'Watch Out!' and pointed to the Bonanza. I looked left and immediately acquired the Bonanza visually; which had begun a hard-left bank; and a descent. I continued to climb; until TCAS announced; 'CLEAR OF CONFLICT.' I leveled the aircraft at approximately 8200 FT. We had flown through the localizer at that time; so ATC issued us a turn to rejoin; and a descent. They also asked; 'What's going on?' We told them that we had responded to an RA for the Cessna; and it had triggered a second RA for the Bonanza. They said that they thought we had the Bonanza in sight; but we advised them that complying with the first RA had generated the second RA. I also requested ATC mark the tape; and we marked an event on our DFDR/CVR. I estimate that we were within 200 FT vertically and approximately 1200 FT horizontally from the Cessna below us; and at the closest point; co-altitude; and less than 500 FT horizontally from the Bonanza. We joined the localizer; and landed uneventfully. No passengers or crewmembers received any injury; although some passengers did mention to the flight attendant after landing that they had seen the aircraft (Bonanza).