Hi, how do I create timer based on certain voltage only

Im doing maintenance calling system project.I want the timer to start counting after the voltage exceeds certain limit.Is that possible?
I have 4 input using modbus and switches.After clicking respective switches the voltage will rise to a certain level.I want the timer to start counting after I clicked the switches.How do I do this?
Already searched on youtube but they only uses inject not voltage as my project.

What have you done so far?

You can store a time within a context value ( see the documentation on function nodes for an explanation)

The cookbook is also worth looking at http://cookbook.nodered.org

Alright thanks bro , ill study the the links. Thanks a lot