Hi Steve,
By looking your screen shot, you have defined an input parameter with name "REGION" and in Script based calculation view, you are using "inregion" instead of "REGION" in placeholder.
If possible, use UPPER CASE "REGION" instead of SMALLER CASE "region" while defining script based calculation view.
Couple of more points:
If you have created a semantic layer using calculation view contains input parameter in BO Information Design tools.Then later when you access the same semantic layer through BI tools then automatically prompt dialog should appears asking for values. OR With universes on a single view it is possible to use the END_SQL parameter where you add the parameters to pass to the view, something like:
END_SQL defined as WITH PARAMETERS ('PLACEHOLDER' = ('$$CURRENCY_CODE$$', 'EUR'), 'PLACEHOLDER' = ('$$DATE$$', '09092007'))
And you can actually use prompts instead of hard coded values.
Please refer this document from Page No 16. [https://scn.sap.com/docs/DOC-27676].
Hope this helps.
Best Regards,
Vaibhav