Vlookup on partially sorthed lists

[Sean]

Hi,

I am using a vlookup function without the false argument on a list
(2400 items) that is mostly sorted, except for a few values (35) right
at the bottom of the list that have a 0 value. I was under the
understanding that the vlookup function stepped through the list until
it came to a value that was greater than the lookup value at which time
it brought back the relevant value from the nominated column to the
right.

On the data I have the function works OK until I try and lookup a value
exceeding row +-2300. At this point the function brings back a 0 which
is the data corresponding to one of the 0 value items. When I delete
the 0 value items off the bottom of the list the vlookup works OK. The
reason the data has a bunch of 0's on the end is that it is a dynamic
list (made up of formulas that refer to other dynamic data).

To replicate
Place 1 in B7 and C7
Place formula "=+B11+1" in B8 and copy down to B2401, copy also to
column C
Place value "0" in B2402 to B2436 and C2402 to C2436
Place value 2200 in D7
place "=VLOOKUP($D$7,$B:$C,2)" in E7
Change value in D7 to 2300 and a result of 0 is returned.
The lookup works for all values less than 2200.

Any assistance or explanation will be appreciated.

Sean