using an expression

Hi,

I am using an expression like this, (2.4 - cross(VDC("/out") 2.4 1 "either" nil nil)), which means the I get the value of y exactly at 2.4 in x-axis, which is finally subtracted from 2.4. This gives/calculates a value for me in the 'value' column of ADE outputs.

Now, i am interested to replace 2.4 with a signal in my simulation. Say, the signal is net028.  I tried something like this,

(VDC("/net028") - cross(VDC("/out") VDC("/net028") 1 "either" nil nil))

and

(VT("/net028") - cross(T("/out") VDC("/net028") 1 "either" nil nil))

but i did not get the value/result :-(

I have three queries,

1. How to use a signal in place of 2.4 in the above expression.

2. I am also interested to do a parametric sweep of that signal and plot it, may be if possible in wave. Is it possible ?

3. As I am playing with low values, is it possible to use cross function with atleast 6 decimal round off ?

Thanks in advance.