tablesorter filter functions - external select box to filter by column

tablesorter filter functions - external select box to filter by column

Using the tablesorter plugin I want to be able to filter entries in a table with a select box. In the examples I could find select boxes in the table header but I couldn't manage to create an external select box which is populated with the values in a specific column (in this case I want to filter by the values in column 3 - Age) and lets me filter the table.

Can anybody give me some advice or did I just miss the example page for this case? I've set up a jsfiddle to give you an idea of what I want to achieve.

Thank you in advance for any help or advice!