Okay, assume your data now starts in A10 and goes down to B19 - the
first formula I gave you should be this in C10:
=A10&"_"&COUNTIF(A$10:A10,A10)
and copy this down to C19. Notice that all the row references are the
same as the starting row.
Suppose now that the number you input is in E5, then the formula in F5
would become:
=IF(ISNA(MATCH(E$5&"_"&ROW(A1),C$10:C$19,0)),"",INDEX(B$10:B$19,MATCH(E
$5&"_"&ROW(A1),C$10:C$19,0)))
and again this is copied down as many rows as you think you might
need.
In a real case your range is likely to be much larger, so assuming you
still have the same columns as I've assumed, then any reference to C
$10:C$19 or B$10:B$19 should be changed to suit your data. If you have
2000 rows, for example, this would become C$10:C$2009. Note that the E
$5 relates to the cell where you want to enter your search number, and
A1 is used for the first row the formula is put in - it will change as
you copy the formula down.
Hope this helps.
Pete