Hasta La Motion!

ultra noob query.

i renderout the zbufferpass via vray in 3dsmax (with default settings)
i apply a Zblur node in nuke.
i keep fiddling the sliders untill i see some seperation (in the focal place mode) and at times i simply cant find it!

now here is my question:
how do i read the onscreen values and get the sliders right @ one go (without have to fiddling around the sliders)?

i hope i was clear in explaining.

also if there is a comprehensive read somewhere out there, i would appreciate a lead!

thanks
m