Pulse width measurement

Hi! I need to measure the pulse width of an incoming signal by using a counter that works at a higher frequency. As the design must be made in quartus, i intend to use the lpm_counter megafunction. The problem is how do I generate the reset signal for the counter? I need to reset the counter on both positive and negative transitions of the incoming signal. And how do I read the counter value before each reset is done?

Thanks.