Power BI User Input for change value dynamically

Hi,

for example I want to calculate the Area of the Circle , so I need to change Radius every time(user should be able to enter value) and calculate Area as following

I tried to create parameter and try to change that value as I want, but above one is not properlly work, please help me to do this one in Power BI and is there any workarround for this one.

Thank you,

Harsha