You can use the set_param command to associate your own data with a block. For example, the following command associates the value of the variable mydata with the currently selected block.
set_param(gcb, 'UserData', mydata)
The value of mydata can be any MATLAB® data type, including arrays, structures, objects, and Simulink® data objects.
Use get_param to retrieve the user data associated with a block.
The following command saves the user data associated with a block in the model file of the model containing the block.
set_param(gcb, 'UserDataPersistent', 'on');