Dynamic calculation

Hi, 

I am trying to create a visual that calculates based on the dynamic value selected in the slider or entered manually.

For example :

In the below image, the calculated is done based on a fixed value coming from the excel. 

I need create a calculation based on the cost they select manully and give them the result. I'm not sure what visual can be used to take the input from the user for the calculation.

Appriciate any help on this ! Thanks !