You could populate the list of values in the dropdown list using a calc that would add values as appropriate for the number of records in the found set, set this into a global field, and then use that field as a the source of the drop down list?
If the number of records is always going to be 15, then you could just manually make a value list with the numbers 1 through 15 and use that?
Either way, once you've got your list of values, the user can select the required records value (again, in a global field) and then use the Go To Record script step to target the appropriate record.
Something along the lines of:
Go To Record [ specify ; GlobalField with Desired Record Number ]
yes you can leverage the script triggers available for a drop down control to fire a script that will change records or do whatever you want.
Right click the drop down control in Layout mode and set script triggers.
Google FileMaker script triggers and you will find a bunch of learning resources