Need to select and update with the same sql statement

List,
I need to do a command like:

select * from "table" where "id"=54; update "table" set "col"=value
where "id"=just selected id

Is that possible? How would I work that into a StoredProcedure? I'm
getting a race condition where two+ clients are asking for data but getting
the same record, (each record is a datachunk for a distributed client).
This results in each client working on the same data, not good. Any ideas?
I'm posting to the php/sql list cause the clients ask for the datachunk via
SOAP request that is processed via PHP. Any assistance would be great

/B