Date comparison question

Hi

I require a query that will see if a stored date is more than a certain 
interval before the current date.  Using an interval of 10 hours, the query 
would be something like:

SELECT * FROM utable
WHERE now() - utimestamp > interval '10 hours';

The problem I am having is that the interval is not fixed, and I would like 
to be able to store it as a value in a database table.  The unit of the 
interval can, however, be fixed, and will almost certainly be fixed to 
hours.

I have not been able to find a way of doing what I require, does anybody 
have any ideas to what I need to do?

Cheers.

Jan.

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