I think you are describing the AutoFilter here. It could be that the filter
is working fine but you have reached the limit of items that can be listed
in the drop-down (a quick test on my Excle shows a limit fo 1000 items, if
you have repeated names then you could come to 5066 in total I suppose).

You should still be able to use the Custom filter. Just hit that little
arrow and select custom, then enter your search criteria using the tools
provided.

Another possibility (less likely from your description) is that you have a
blank line in your list. The Auto Filter stops at blank lines.

If you want to search for cells with formulae in them, just select Go To
from the Edit menu, click on the Special button and select Formulas. You can
get Excel to serach for all cells containing a formula in this way.

Lastly, if you think there might be a formula with the number 5066 in it,
you couldjust search for the number 5066.

Good luck.

Thomas.