[otrs] otrs stats first response time

Hy all, I'm knocking my head off working on : - creating a custom stat query which return for all tickets in a definied queue, the first response time. - creating a custom stat query which will return number of tickets in a definied queue who are below the first response escalation time and those who are +after the first response escalation time. anyone have already done that or know how to create the custom stat ? Thanks for your help, Rachid