I figured it works like this:
x.addlistitem( "col1, row1", 1, 1 )
x.addlistitem( "col2, row1", 1, 2 )
x.addlistitem( "col3, row1", 1, 2 )
x.addlistitem( "col1, row2", 2, 1 )
x.addlistitem( "col2, row2", 2, 2 )
Thanks