B737-300 FO IS CONCERNED PERFORMING THE PRE-TKOF CHKLIST WHILE BACK-TAXIING ON THE RWY TO THE DEP END SUBJECTED THE FLT TO A CONFLICT WITH AN INBOUND ACFT.

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GEG DEP TXWY A (ON THE TERMINAL SIDE OF RWY 21) WAS CLOSED FROM A3-A6. GND ADVISED US TO BACK-TAXI ON RWY 21 AND CONTACT TWR. I FIGURED THEY WOULD HAVE US PULL OFF THE END TO FINISH CHKLISTS. WE CONTACTED TWR RIGHT AWAY AND SHE INSTRUCTED US TO TAXI INTO POS AND HOLD. AT THIS POINT WE HAD JUST ENTERED THE RWY AND WERE MAYBE 3000 FT FROM THE END. I ASKED THE CAPT IF HE WANTED TO DO THE CHKLIST ON THE RWY. I REMEMBERED THAT CHKLISTS SHOULDN'T BE DONE WHILE XING A RWY; BUT WASN'T SURE ABOUT 'BACK-TAXIING.' THE CAPT SAID YES; IT WAS FINE. ABOUT 1/2 WAY THROUGH THE CHKLIST; THE TWR CTLR INTERRUPTED AND SAID 'I'VE GOT A DASH 8 ON 3(?) MI BASE; FLY RWY HDG; CLRED FOR TKOF RWY 21.' AND WE WERE STILL BACK-TAXIING NEBOUND! BOTTOM LINE: THE CHKLIST WAS FINISHED AND THE TKOF WAS COMPLETED WITHOUT AN ADVERSE EVENT. I COULD SEE FROM THE TCAS THOUGH; THAT THE DASH WAS NEAR FLARE AS WE ROTATED (TCAS SHOWED RELATIVE ALT DIFFERENCE OF 100 FT (YELLOW 01) BEHIND US). I THOUGHT ABOUT SAYING SOMETHING TO THE CTLR AS WE DEPARTED; BUT DIDN'T. SUGGESTIONS: THERE WAS A PERFECTLY GOOD TXWY (TXWY G) ON THE OTHER SIDE OF THE RWY WE COULD HAVE USED; OR EVEN BETTER; USED TXWY F TO TXWY A TO GET BEYOND THE CLOSURES AFTER A SHORT BACK-TAXI. WHILE WE KNEW PRIOR TO TAXI THAT A3-A6 WAS CLOSED; ASKING GND WHAT WE COULD EXPECT FOR TAXI PRIOR TO PUSHBACK WOULD ALSO HAVE BEEN HELPFUL. NEXT TIME I WILL ADVOCATE TO THE CAPT THAT WE NOT DO THE CHKLIST WHILE OF ANY RWY; XING OR BACK-TAXIING. I WOULD RECOMMEND THE FOM BE UPDATED TO INCLUDE NOT COMPLETING CHKLISTS WHILE BACK-TAXIING (I COULDN'T FIND A REF TO THIS). LASTLY; TWR CTLRS NEED TO BE EDUCATED ON AIRLINERS AND THEIR CHKLIST/TAXI PROCS.