Yes, was going to suggest this if the line is didn't work. Came to mind after I posted previously. I use that exact model on a computer to get an extra line in. That should solve your problem,
@Saint and
@Kelita
But, to answer the "how do you get a line in" question, your computer should have a jack on it somewhere that is a line in or can be a combo line in/headphone jack. But not all headphone jacks are a combo. If in doubt, the USB thing is a handy way to go. Then you connect line from the scanner to the purple/pink jack and you're good. It will then show up as an input in the Windows sound settings; verify that before working with ProScan.