Hi vijayansiva,
It seems your goal is the last case in my blog (the Note in the section 3. Y-shared Double-X with Fig.9).
http://blog.originlab.com/graphing/how-to-make-a-neat-double-x-graph
Specifically, you can follow the following steps:
1) Highlight A(X1) and C(Y2), and make a plot. Scale the (bottom X) as you like.
2) "Graph: New Layer: Top X(Linked Y scale & Dimension)"
3) Double-click the plot to show the Plot Details dialog, and select the TopX layer node
in the left panel, and select "Link Axes Scales" tab.
4) Select "Straight(1 to 1)" for X Axis Link, and press "Apply" buton. In the same tab,
select "None" for X Axis Link again, and press OK to close Plot Details.
5) Double-click the TopX axis to show the Axis dialog box for Layer2, and set:
Scale tab> Horizontal> Major Ticks: Type=By Custom Positions; Position=col(A).
Tick Labels tab> Top> Display subtab: Tyoe=Tick-indexed dataset; Dataset Name=col(B).
Click OK to close the dialog.
This produces the graph below:
The layers are not linked, so if you rescale the layer1, you need to redo the steps 3-5).
Hope this helps,
--Hideo Fujii