Do you mean in Report Designer?  If so, the Min() function or aggregate function will give you the lowest value in a set of values.
eg. If you want the footer section of a report to show the minimum UseByDate of the TraceableItems in the Detail section, put TraceableItems.UseByDate in the footer and set AggregateFunction to Min.

If there are blank values for UseByDate, you will need to use an expression like:
TraceableItems.UseByDate > #0001-01-01# ? TraceableItems.UseByDate : #2099-12-31#
which replaces blank UseByDates with a date well in the future,