Hi
Sounds like a bit of a tongue twister, but a formula involving VLookUp
would probably do the job?
On the second sheet in a third column for the first user type
=VLookUp(user, FirstRange,2,False)
where
user = address of first user (A1?)
FirstRange = Range on first sheet containing the two columns of data.
Use absolute referencing like Sheet1!"$A$1:$B$20" after selecting range
with mouse/keys.
2 refers to the second column in the FirstRange with the paths
False just means you don't have to sort.

This will give the new path if the user is already in Firstrange and
#NA if they are not.
Now in a fourth column on the second sheet you might do (in D1?)
=if(ISERROR(C1),B1,C1)

where I'm assuming the first user is in A1 so that his path is in B1
and his VLookUp in C1.
Now copy down this formula and copy/paste special...values only into
the second column. delete columns 3 and 4 and you are done.
Not sure that is exactly what you want, but you should be able to bodge
it to fit.

regards
Paul