How to use a calculated field in a control?

[smithgce]

The above describes how to connect a calculated field to a filter, not a control.

This is the best answer I have found:

Passing value from calculated field to a parameter

Hi, you can create a calculated field in data prep phase, and when you add a parameter in analysis, you can link the parameter with the calculated field. Curently calculated field created in analysis are not available to be linked by a parameter.

For some reason, creating a calculated field through the data source rather than within the analysis allows it to be connected to a parameter later on. To use a calculated field with a control and parameter, created the field through the data source page and proceed as usual.