Hi,
To change the position of inport block you are supposed to use get_param and set_param.
block_size = get_param('model_name/block_name','Position');
X = block_size(1,1);
Y = block_size(1,2);
X + Width = size_blk(1,3);
Y + Height = size_blk(1,4);
set_param('model_name/block_name','Position',[X Y X+Width Y+Height]);
for example :-
set_param('vdp/Fcn','Position',[50 100 110 120])
You can refer to this link for more information set_param.