B737 FLT CREW DISTRACTED BY MULTIPLE COCKPIT ACTIVITIES FAILS TO RECOGNIZE RTE DISCONTINUITY RESULTING FROM ATC RWY CHANGE. CREW FAILS TO MEET TRACK AND AIRSPD REQUIREMENTS OF THE GLEN ROSE STAR TO DFW.

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WHILE ON THE GLEN ROSE EIGHT ARR INTO DFW IN VMC CONDITIONS AT 10000 FT MSL; WE WERE ASSIGNED TO CROSS DELMO AT 250 KTS AND TO EXPECT RWY 18L FOR LNDG. THIS REQUIRED A REPROGRAMMING IN THE FMC DUE TO US HAVING RWY 17C IN THE BOX. UPON EXECUTING THE RWY 18L IN THE FMC IT CREATED A RTE DISCONTINUITY IN THE FMC AFTER HIRST INTXN THAT WAS NOT SEEN IMMEDIATELY. IN ADDITION; THE PNF WAS ANSWERING A CALL FROM THE FLT ATTENDANTS AND WAS NOT 'IN THE LOOP' OF WHAT ATC HAD ASSIGNED AND THE CHANGES MADE IN THE FMC. THINKING THAT WE WERE AT DELMO; I USED HDG SELECT AND TURNED THE AIRPLANE TO A 355 DEG HDG AS STATED ON THE ARR. ATC QUESTIONED OUR HDG AND ALSO OUR 250 KT AIRSPD SO FAR FROM DELMO. WE THEN REALIZED THE ERROR AND THE RTE DISCONTINUITY WAS CLEANED UP AND ATC ASSIGNED US 300 KTS DIRECT TO DELMO INTXN AGAIN. OF COURSE ALL THIS WAS HAPPENING WITH SEPARATE CTLRS AND AFTER JUST DEVIATING AROUND TSTMS. THE CAUSE OF THIS PROB WAS PLT ERROR AND NOT CHKING THE RTE. CONTRIBUTING FACTORS INCLUDE: 1) SITUATIONAL AWARENESS CONCERNING OUR POSITION ON THE ARR. 2) DISTRACTIONS OF THE FLT ATTENDANTS CALLING; ATC CTLRS ISSUING DIFFERENT CLRNCES. 3) FATIGUE -- AT THE TIME OF THE INCIDENT WE HAD BEEN ON DUTY APPROX 12 HOURS AND OVER 8 BLOCK HOURS OF FLYING DUE TO WX DELAYS.