Cadence Calculator Function for the difference between the abscissa of the intersection of two curves

Hi,

I am running a dc simulation for Schmitt Trigger .

Its voltage transfer characteristic curve is shown in the following figure (the green curve  V=Vout ).And the red curve(V=Vin) has a slope of 1 .

I would like to find the difference between the abscissa of the intersection of two curves, which represents the hysteresis width of the Schmidt trigger.

Then I want to do a Monte Carlo simulation of hysteresis width.

So far I have ymin(abs(v("/vout" ?result "dc")-v("/vin" ?result "dc")))  obviously.

However, ymin(abs(v("/vout" ?result "dc")-v("/vin" ?result "dc")))  is not equal to zero but a very small value .I think it has to do with step size.

Is there a calculator expression for what I want to do?

My virtuoso version is 6.17-64b.

Thanks