Check if a program exists and if not to install it
<p>I am writing a Jenkins build with an NSIS file. I need a script to check if the device has a certain program installed on it and if it doesn't, it should install the .exe's from the installer folder. I have all the .exe's in the install folder required for the installer to work.</p>

<p>This should be rather simple but i am baffled in this case and could not find any information about this anywhere.</p>