Shelly -
If you have a legacy dual LNB on that 61.5 dish there is no need to put up a second one for VOOM. Just split the signal with a standard multiswitch first, sending one output to your VOOM box and another to one input leg of an SW21. The other input of the SW21 should be an output from an SW64 or twin/quad LNB from your Dish500. The output of the SW21 goes to your Dish box. Voila - you have 61.5, 119, and 110 on the Dish box and 61.5 on the VOOM box. There are other ways to do this but this is the simplest. If you have more than one box for either service you may need a slightly more complex setup.