Hi

I am trying to enhance a mdx query that has parameters by adding multiselect function.

Hi Kmogodi, 

According to your description, you want to add a multiple-values parameter to your dataset mdx query, right? 

In Reporting Services, we can use report parameter which has multiple values to control the dataset result. For your requirement, please refer to this blog: SSRS How-To: Simple Method to Pass MDX Multi-Select Parameters to MDX Datasets. 

If you have any other question, please feel free to ask.

Regards,
Shrek Li