How to use interpolation function in parameters?

Dear users,

I have defined a piecewise function from a file with function name 'functionName' in Global Variables.

I would like to define a parameter that uses this function in Global Definitions -> Parameters. For example:

newFunction = functionName(parameter1)*parameter2

where parameter1 and parameter2 are also defined in Global Definitions -> Parameters. Moreover parameter2 is used in a parametric sweep study. At the end of the study I would like to plot newFunction vs parameter2.

The problem is with the definition of 'newFunction'. Because of 'functionName(parameter1)' it is highlighted in red.

DO YOU KNOW HOW TO USE A PIECEWISE FUNCTION defined in Parameters for the definition of another parameter?

Thanks