Hi Umesh,
In order to modify some dialog parameter value, you can find out the actual parameter name in the following way:
>> path = 'model_name/Simulink_Function_block_name/trigger_port_block_name';
>> get_param(path, 'DialogParameters');
This will give you all the dialog parameters for the block that can be modified programatically using the get_param, set_param functions.
For a trigger port, inside the Simulink Function subsystem block, you will find a "FunctionVisibility" property. You can set its value using the set_param function:
>> set_param(path, 'FunctionVisibility', 'global');
