This would need to be accomplished through a custom PX policy
We have an example PXpolicy in: C:\Program Files (x86)\CA\Identity Manager\IAM Suite\Identity Manager\tools\samples\PolicyXpress\RandomPassword
Please see the readme in that directory and I have pasted below.
Set random password sample policy What does it do? In many cases, when users are created, they are given a generic or random password. This is because the person who creates the user should not know what the password would beis, for security reasons. This sample policy will generate an 8- characters random password and assign it. This happens when submitting the "Create User" task. For testing purposes, there will also be a message in the log specifying the user and password. For example: *** Random password for user nisyu10: LQ1gHDm2 To use this sample: There are a few steps to make this sample work in the application: 1. Using the IM webdentity Manager User Cconsole, select the environment and open "roles and tasks settings". 2. Click on import, and select the file RandomPasswordSample.xml 3. Click on the restart button. At this point the policy can also be viewed or edited from the Policy Xpress menus.