How to check any condition before installation pro

问题:

I am making a setup of windows application. In setup process i added a screen using user interface dialog properties and taking some input from user and want to put condition like this:

if(value_is_correct)
{ 
   Continue_setup;
}
else
{
   Rollback_setup;
}

Somehow my objective is complete but I want to rearrange the steps of process :

1. I ask user to enter value(password)
2. User clicks on next
3. Next dialog screen appears, Setup process get started and in between that process it shows that password is wrong and it again Rollbacks the setup.

These images shows the process clearly:

My question is :How to check the condition on click of Next button of Password form.(First Image). It should not start the installation process.

Please provide any solution or any useful link. Thanks.