Simulink block for maximum ABS over last XX seconds

I'm working with a simulink model that has a transfer function outputting a signal. For another calculation, I need to know the maximum amplitude of the output over the last XX seconds. I know I can use an ABS block but then I need something that will grab and output the largest value over the last XX seconds. I'm using ODE45 with variable step size so I need something that doesn't rely on the # of samples.

Any help would be appreciated.