DAX query with page level slicer

Hello,

I'm fairly new to DAX querying and have a question from the business about using a page level slicer within a DAX query, instead of a hard coaded value.

Below is what I'm trying to accomplish:

Original code:

No. of Activities = COUNTAX(
                 FILTER(
                    RELATEDTABLE('Customer Events'),
                    'Customer Events'[Activity Type] = "Complete Purchase"
                    ),
                 'Customer Events'[Activity Type Count]
                 ) + 0

Modified code:

No. of Activities = COUNTAX(
                 FILTER(
                    RELATEDTABLE('Customer Events'),
                    'Customer Events'[Activity Type] = 'Customer Events'[Activity Type Cnt]
                    ),
                 'Customer Events'[Activity Type Count]
                 ) + 0

What I'm trying to do is show the number of repeat purchase activity by count.

Any information you can provide me with would be much appreciated.

Thank you