matlab simulink masking check box

I am trying to mask a subsystem (controller) I am building. I have two signals (signal A and signal B) inside the subsystem. I want the user to have the capability to select the signal they want to output from the subsystem. For example, consider signal A to be a DC signal of value 1, and signal B to be a DC signal of value 2. These values are predefined. The user will not have access to change the signal, but only the capability to switch from one to another.

I want to create a parameter in the mask (a checkbox particularly). If the user selects the checkbox, signal A will be selected as the output. If the user unchecks the checkbox, signal B will be selected as the output.

Any help will be appreciated.