Use ultrasonic sensor to indicate the exact time an object passes by

Hello,

I am having some trouble here. I am using 2 ultrasonic sensors to detect as an object passes by the first sensor and again by the second one. What I want to do is calculate the time of which that object takes to get from the first point (where the first sensor is) to the second point (second sensor). However, I cant find an Arduino function that gets me the time.

Any suggestions?

Thank you

However, I cant find an Arduino function that gets me the time.

millis()