Extracting the script from a column, creates a script that will recreate a new column. If you want to move values from one data table into a column in another table, where the column already exists, you might want to use something like the code below
dt = Open( "$SAMPLE_DATA/Big Class.jmp" );
theValues = column(dt, 1) << get values;
dt << Select Where( Row() == 1 );
d3 = dt << Subset( Selected Rows( 1 ), selected columns( 0 ) );
d3 << add rows(nitems(theValues)-1);
column(d3,1) << set values(theValues);
Jim