the question of installer(help me !!)

Is it possible to easily setup a launch condition that checks if another
product is installed on the system?

 

  Firstly ,I descript the function steps installer.

1. We must check  lisence is installed before the installation of  application.
2. if lisence is  setup then  application directly.
3. if lisence isn’t  setup then lisence will install  before the application automatically.

 

i use search for Registry key and value , launch condition to check  if  the machine is install the Lisence .the result is right.

but i question is that : 

   if  installer package is checked that  lisence isn’t  setup then install the  lisence ,but after complete the installion of lisence  installer can't return to install the application???