Automatic PDF Reader Selection

I'm currently working on a program called DocEar Portable and it has the option of relying on a PDF reader. In general, all it does is look at the ones installed on the system and then lets you pick, but I was able to track down the line in the preferences file and I was wondering if there was a way of using the custom.nsh file to see if Foxit or Sumatra Portable are installed and putting them in the preferences file by default. Below is the preferences part. Any help would be nice, if possible.

docear_open_on_page_reader_command=C\:\\Program Files (x86)\\Foxit Software\\Foxit Reader\\Foxit Reader.exe*"$FILE"*/A*page\=$PAGE

Update: I also ran across the following code further up in the preferences file that might aid things somewhat.

installed_pdf_readers=C\:\\Program Files (x86)\\Foxit Software\\Foxit Reader\\Foxit Reader.exe|C\:\\Program Files (x86)\\Adobe\\Reader 11.0\\Reader\\AcroRd32.exe|