find a value in Y channel corresponding to a value in X channel

[GDU]

I have two channels Y & X i want to find out the value of channel Y at some value of X. And Channel X need not to have that crisp value. Like i want to find out the value of Y at X=0 and X may have value like 0.001 or -0.05 then it should consider the nearest possible value to X=0 and fetch out the value of Y. Like there is function VLOOKUP & HLOOKUP in MS excel.

NOTE: And these X & Y channels are created from other channels using Approximation, Differentiation

[GDU]

Don't worry GOT IT

its PNo(channel, value) it returns the row no and use that row no to find value in other channel CHD(row, channel)

Tell me if i am going wrong or if there is another shortcut to this