how to get a sum of all columns with names stored in a list

[#1]

I have create a list of column containing roughly the same name below:

Xlist = {};
Ylist = {};
for(i = 1, i < ncols(dt2), i++,
if(
contains(dt2:i<< get name, "XXX") > 0, insert into(Xlist, dt2:i<< get name),
contains(dt2:i<< get name, "YYY") > 0, insert into(Ylist, dt2:i<< get name),
)
);

I would like to create a new column as below which will give me a sum of the Xcolumn and Ycolumn. It is not working well for me at all. I must not be doing something right.... Please help.

dt2 << New Column( "Xsum", Numeric, Continuous, Format( "Best", 12 ),
Formula(
sum(eval(Xlist)),
)
);

[#2 · Accepted solution]

This discussion is a duplicate of the discussion item

Adding up all the columns with names stored in a list