Assigning Inputs & Outputs in Mathcad

Consider that, I have a data based upon the below image and I`d like to integrate that data with Creo so that I could sync up both. 

Now, "Number of Active Coils: Nc:=1" is assigned as input and the "Diameter of the wire: dw:=1mm" is taken as output. 

The issue I`m getting is that, I`m able to change the value of output as many time possible, but once if I assign a value as an input, it indirectly gets locked... Changing that value is impossible. 
What could be the reason for this? Am I missing something, or is there something wrong with the settings of my workstation..? Please clarify.

- Srikar