Select Where 'in' A List

I have done queries before where you have something like this:

 Select name
From people
Where uid in (Select UID from employees where salary > 500000)

 as an example.

I have to use stored procedures, I can't connect directly...

I have a datatable of records that I select from a database. In the database table there is a flag 'checkedOut' (bit field) wich I want to set to true (1) for each of these records.

Since I have to use stored procedures I think I am limited to passing in parameters. I wrote a function using a stringbuilder to concatonate the key fields into a comma delimited list "1, 55, 98" etc. and thought to use it as the clause in the 'in' sample ie:Update ServiceRequests set
CheckedOut = 1
Where UID in (@UIDList)


 I have tried a few different things, none works.

Any ideas how you might accomplish this with stored procedures?

The records are passed to a thread to be dealt with and it's possible the next time it runs it will pick up the same records for processing if the first thread isn't through. I needed the 'CheckedOut' to ensure I don't accidentally do that.

Thanks.