Hi Gustavo,
Can we just back up a touch. You have created a mapping at the /Events level - the top of the Event Class tree. I would be far more tempted to create your new class further down the tree. Your original event appears to be of class /Win so I would suggest you create either a mapping at the /Win level or I personally would create a new event subclass there. So, go to the Event Classes panel, navigate down /Win and then use the dropdown beside "SubClasses" to "Add New Organizer". You can call it whatever you like - Microsoft-Windows-DHCP-Server would be a good candidate. That gets you a new class. Reason for creating a whole new class is that it makes it easier to then create alerts (emails, pages,..) that select on that particular problem. This new class isn't essential but i would suggest it may serve you well in the future.
Now you want to move the mapping that you have created from /Event to /Win/Microsoft-Windows-DHCP-Server. Simply navigate to your mapping, click the selection box alongside and use the dropdown menu to Move Mappings.
Check that your specific events now map to this new class.
Your screenshot shows the transform in red. This means that there is a problem with it - probably some sort of syntax error.
Do you have a colon at the end of each if statement (I can see you have on the first but can't see the second)?
Python is very picky on its indentation. It doesn't matter how many spaces you have at each level of the structure but it must be the same number of spaces.
Cheers,
Jane