unsorted lookup vector in LOOKUP

Hi,
=LOOKUP(L39,{"100/30","130/30","160/50","200/50","250/50","300/50","350/50","40/40","60/30","80/30"},{4,5,6,7,8,9,10,1,2,3})

In the above formula, lookup vector is sorted and the corresponding values are returned. But I want to use unsorted lookup vector. My formula should look something like

=LOOKUP(L39,{"40/40","60/30","80/30","100/30","130/30","160/50","200/50","250/50","300/50","350/50"},{1,2,3,4,5,6,7,8,9,10}).

How can I write the lookup function with unsorted lookup vector.

Thanks