This is a very simple thing for one to do in JSL. Below is my version of the code. I don't know what the name of the column is that you want to change the values for, so I am just calling it "theColumn". I really haven't tested the code, but I am pretty sure it will work
Names Default To Here( 1 );
dt = Current Data Table();
For( i = 1, i <= N Rows( dt ), i = i + 14,
For( k = i + 1, k <= i + 13, k++,
dt:theColumn[k] = dt:theColumn[i]
)
);
Jim