if condition with vlookup and left

I facing issue with Excel IF formula along with Vlookup function.

1st requirement -if a cell S2 is 9999 then take 1111 or 2222 2nd requirement - if a cell S2 is 9999 then look for the cell O2 of left first 5 characters if it matches then take value as 3333 or 4444

=IF(OR(S=9999,1111,2222),IF(S2=9999,VLOOKUP(LEFT(O2,5),lookups!$AS:$AU,2,0),VLOOKUP(LEFT(O2,5),lookups!$AS:$AU,3,0)))

Error message #Name?