InstallShield LE - getting a registry value

I'm still doing a search/research into this, but here's the deal:
I'm upgrading an old utility. It was originally done in VS2008, VB.NET, FW2.0, 32 bit... I need to make it compatible with the latest version of one of our products, which is 64-bit and running FW4.51 minimum. OK, so there's two DLLs, and EXE and a setup in the project. VS2008 only supports up to FW3.5 ... not good enough, so I ran the solution through VS2015 and it upgraded the DLLs and EXE projects no problem and threw the setup back out at me and unconvertable. Fine. No problem, I have InstallShield LE that I used on another project, I can use that here, too right? Not so fast.

One of the quicks of the project is that it has to install into a specific folder of ANOTHER application. So it needs to go to the registry, get the install path of that application and use that as the root app folder when installing this utility. That's where I'm having a problem. I can see how to check for a registry value as a prerequisite, I can see how to create registry values during installation, but what I don't see is a way to look up a regvalue, store it and then use it later as the root install path.

So far my google-fu has returned results on how to check it, but nothing (yet) on how to store the value and re-use it later. If anyone knows how to do this, or simply point me in the right direction (my next stop is the flexera forums to see if there's something in there that might help) of if it is something that just isn't possible in ISLE, if they could let me know, that would be great.

-tg