Multiple curves manipulation

Hello, 

I have 2 sets of data in terms of time and want to add them respectively.

To make the problem simple, there are Shear T and Shear S for 3 beams elements in terms of time. I want to get the sum for each beam separately.

My first resort is the Macro.

I have written a Macro but found it can only select values one by one. Is there anyway I can use a macro to deal with these 3 lines all together?

Or is there any other suggestion to plot the result all together instead of one by one operation? The real data is very large

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