B737-300 FLC MISPROGRAMS FMS ON RECEIVING DSCNT CLRNC CHANGE AND HAS AN ALTDEV.

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WE WERE FLT PLANNED TO ARRIVE DFW VIA THE BOWIE (UKW) ARR. FMS WAS PROGRAMMED TO CROSS KAJAY INTXN AT THE EXPECTED ALT OF FL240; AND ALSO PROGRAMMED TO CROSS BAMBE INTXN AT 11000 FT. PRIOR TO REACHING THE UKW 287 DEG RADIAL; IN THE VICINITY OF TXO; WE WERE RECLRED DIRECT UKW; WHICH ELIMINATED THE FMS PROGRAMMED DSCNT TO FL240 AT KAJAY. FMS DSCNT PROFILE IS NOW COMPUTED TO CROSS BAMBE AT 11000 FT. WHILE PROCEEDING DIRECT UKW; WE WERE CLRED TO CROSS 40 DME W OF UKW AT FL240; PLT DISCRETION. WE REPROGRAMMED THE FMS WITH A NAV POINT 40 DME W OF UKW; BUT APPARENTLY FAILED TO INCLUDE THE ALT CONSTRAINT OF FL240; SO THE FMS DSCNT PROFILE WAS PREDICATED ON REACHING BAMBE INTXN AT 11000 FT. THE REASON FOR THIS OVERSIGHT IS UNKNOWN; BUT PROBABLE CAUSES ARE CREW INVOLVEMENT WITH ARR PROCS (APCH BRIEFING; CONTACTING COMPANY FOR GATE ASSIGNMENT; ETC) AND DISTR DUE TO A CALL FROM THE LEAD FLT ATTENDANT TO RPT CABIN MAINT DISCREPANCIES OR PAX SPECIAL ASSISTANCE REQUESTS UPON ARR. IN ANY CASE; THE FMS VNAV FUNCTION INITIATED ITS DSCNT ACCORDING TO THE PROFILE FOR MEETING THE BAMBE AT 11000 FT RESTR. WHILE IN THE DSCNT; CTR SUBSEQUENTLY CLRED US TO CROSS BAMBE AT 11000 FT; WHICH LEGALLY CANCELED THE 40 DME AT FL240 RESTR. APCHING THE 40 DME FIX; WE REALIZED WE WERE TOO HIGH TO REALISTICALLY MEET THE PREVIOUS RESTR; AND QUESTIONED OURSELVES AS TO WHY WE WERE IN THAT POS; AND THE MOST LOGICAL REASON WAS THAT WE PROBABLY FAILED TO ENTER THE ALT CONSTRAINT INTO THE FMS AND FAILED TO BACK IT UP WITH RAW DATA NAV DUE TO CREW PREOCCUPATION WITH ANCILLARY DUTIES. LESSON LEARNED IS NOTHING NEW: THE PRIORITIES ARE 1) AVIATE; 2) NAV; 3) COMMUNICATE; AND 4) CHKS.