Locating First and Last Cell Containing a Specific Value

[gooberp00h]

Hello,

I have data in several columns, the first being a date and timestamp
and the second being an identifier (numeric). The numeric identifier
occurs repeatedly at different times (each identifier appears in
numerous rows).

I would like a way of extracting the timestamp of the first and last
occurrence of an identifier.

A:A contains Timestamp
B:B contains Identifier (not unique)

Ideally, given a particular Identifier, I would like to write a formula
that would return the timestamp of its first occurrence and another
that would return the last occurence.

I've tried multiple suggestions including ADDRESS and various LOOKUPs,
but no luck yet.

Thanks for any suggestions!

 

[Gary''s Student]

1. sort the data by column A (the stamp)
2. autofilter by column B (the ident)
the first visible entry is the first value that last visible entry is the
laster entry for that ident