B737-500 CREW EXCEEDS 250 KTS BELOW 10000 FT IN IAH AIRSPACE.

Narrative

APCHING IAH FROM THE NW; WE HAD BEEN CLRED FOR THE COAST ARR; DIRECT TO HOAGI AND ASKED TO KEEP THE SPD UP UNTIL REACHING 10000 FT; AND NOT TO SLOW TO 250 KTS UNTIL THEN. 6000 FT HAD BEEN SET IN THE ALT WINDOW AS THE LOWEST ALT ON THE COAST ARR WHEN WE WERE INITIALLY CLRED FOR THE COAST ARR. WHEN ASKED TO KEEP THE SPD UP; THE FO (HE WAS FLYING) DISENGAGED VNAV AND SELECTED VERT SPD. THIS TOOK PLACE APCHING HOAGI AND JUST PRIOR TO HDOF TO APCH. (AIRSPD 310 KTS; VERT SPD 2000 FPM.) WE HAD THE COMPUTER SET UP FOR THE COAST ARR AND RWY 26. WHEN WE CHKED IN WITH APCH; HE CLRED US DIRECT TO VETTE FOR THE RWY 14L APCH. WE HAD NOT YET REACHED 10000 FT AT HOAGI. BY SELECTING DIRECT TO VETTE AND RWY 14; WE REMOVED THE COAST ARR AND OUR 10000 FT PROTECTION. WHILE THE FO WAS REPROGRAMMING THE COMPUTER; I WAS RETUNING THE ILS AND CHANGING THE INBOUND COURSE ON THE MCP. WE BOTH LOOKED UP AT THE SAME TIME AND WE WERE DOING 310 KTS AT 9000 FT. THE FO DISCONNECTED THE AUTOPLT AND ARRESTED THE DSCNT AND AIRSPD.