Ok, I found the problem (really strange by the way...) My script was not working because it needed another script to work.. As my original script was not working, I created a new one (another powershell script) which was only displaying a form : [CODE][System.Windows.Forms.MessageBox]::Show("My Custom Action","Hello", 0, 64)[/CODE] I removed my original script from the sequences and I have been trying to run my test script at all positions in the UI and Exec sequences With no success.. So, I tried to run my first script again, but I forgot to desactivate my test script And, miraculously, it works ! I don't know if it is an Installshield problem or maybe a wrong defined or forgotten parameter But the fact is, in order to run a powershell script (before install process in my case) follow these steps: For the new script 1) Create a new Powershell custom action (in addition to your script) 2) In the common tab : PowerShell Script File Name -> Path to an empty script ps1 Return Processing -> Synchronous (Check exit code) In-Script Execution -> Immediate execution Execution scheduling -> Always execute Install UI Sequence -> Install Exec Sequence -> + Install Exec Condition -> Not Installed For your custom script In the common tab : PowerShell Script File Name -> Path to your script ps1 Return Processing -> Synchronous (Check exit code) In-Script Execution -> Immediate execution Execution scheduling -> Always execute Install UI Sequence -> Install Exec Sequence -> + Install Exec Condition -> Not Installed If, for example, you add a form in the new script, it will not be executed, but allows the second one to run.. If someone has an explanation, feel free to share ! Thank you and enjoy ... View more

chad.petersen wrote: The Exec Sequence does not happen until you get all of the way through the UI Sequence. It sounds like you've got it scheduled to run in the wrong sequence for what you are wanting. Try changing it to the UI Sequence instead. Chad I have already tryed to change the UI Sequence, it's not working Any other idea ? ... View more