Writing MODBUS register with script

All I need to do is write any number between 0 - 15 to holding register 43437 (2 byte unsigned). Of course I can do this through watchlist or control but I'd like to have a button, or combobox for user interface simplicity.

Right now I am trying using the writedatapoint method but not having any luck getting my script to execute.

Does anyone have a simple "write basic register" code? Even just a 'click this button to make register 43437 a 1' should be enough to get me going.

Any help would be greatly appreciated.