where is OnReadyStateComplete?

Hey,

I feel kind of foolish but how do I use onreadystatecomplete? I read about it here: http://crmbook.powerobjects.com/extending-crm/introduction-to-extending-microsoft-dynamics-crm/form-event-programming-overview/

But when I look at my events it's nowhere to be found.

I want to execute some JavaScript once the subgrid/iFrame is loaded.

Kind Regards