How to select variant within a model reference?

I have a variant block that's within a model reference. I'd like to be able to control which variant is selected from a mask pop menu on a block that contains the model reference, but I can't figure out the proper functionality to accomplish this. If the model reference is a subsystem block instead of a model reference, then I can put code in the pop menu mask parameter's callback code to set the "LabelModeActiveChoice" on the variant block.

I have tried:

1) Using a Subsystem Reference block. This doesn't work, as I get a "Incorrect to modify Subsystem Reference block using callback code" error.

2) Piping the selection via a parameter on the model reference block and putting callback code on a initialization code of a mask on a block containing the variant block. This break because it's trying to change the variant during model init.

Answer 1

[Fangjun Jiang]

Combine this with model parameter for the model reference?

https://www.mathworks.com/help/simulink/ug/mask-a-variant-subsystem.html

Also, note the following.

"The operands that you specify in a condition expression of type Simulink.VariantExpression must be defined in the base workspace or a data dictionary. Specifying operands that are defined in the mask or model workspace is not supported."

from https://www.mathworks.com/help/simulink/slref/variantsubsystemvariantmodelvariantassemblysubsystem.html