OK, I found kind of a hack.
I put the 'fund'-dimension next to the 'value'-measure in 'rows' in the left graph and then hided the title, so you couldn't see anything of it. Then I could select the fund field in the highlight action window.
Now it highlights the fund on the right when you hover over the graph. Not exactly what I wanted, I wanted it to happen after using the drop down menu, but I put a line in there telling people to hover over the graph.