There is information on how to attach dashboard blocks programmatically here (for the Knob dashboard block, as an example) and here (for the data type). You have to create a Simulink.HMI.ParamSourceInfo object. At a minimum you have to set the BlockPath member of that object to the path to the block you want to connect. Depending on which dashboard block you're trying to use, you may need to set other parameters as well.
Other information will depend on the specific dashboard block you want to use and how you want to use it. In some cases (with the Knob, for instance), the value you set through the dashboard block is propagated directly to the target parameter, so it's not actually stored in the Knob block.
