Depending on how you have your calculated table set up, you may be able to create a new Metric (or modify an existing Metric) in the Calculated Table Properties with the "Basic math operations" > "Operation on column and value" option:

Then, you can reference a global table (and probably other tables like statistics collectors) as the value:

Or, if you want to directly edit the query in your calculated table, you can do this:
SELECT
([Column 1] * {Table("GlobalTable1")[1][1]}) AS [Metric 1]
FROM [DataSource]
Where anything between the curly brackets, { }, is assumed to be FlexScript that is executed when the query is called.
You could also create a second calculated table that uses the first calculated table as it's primary table and set up the same kind of metrics as above. But this will all depend on how you have your calculated table set up in your model. So if you can't get it to work and need more help, please attach an example model and/or give us some more details about your model.