Adventure Creator version: 1.85.5

Please test the newly added Formula functionality before releasing it.
I had to modify your code to get it to work successfully.

Static\Enums.cs
Line 120:

public enum SetParamMethod { EnteredHere=0, Random=2, CopiedFromGlobalVariable=1, CopiedFromLocalVariable=6, CopiedFromComponentVariable=5, CopiedFromParameter=3, CopiedFromAnimator=4, Formula=7 };

Actions\ActionParamSet.cs
Line 414:

switch (_parameter.parameterType)
{
    case ParameterType.Float:
        floatValue = (float) AdvGame.CalculateFormula (runtimeFormula);
        _parameter.SetValue(floatValue);
        break;

    case ParameterType.Integer:
    case ParameterType.PopUp:
        intValue = (int) AdvGame.CalculateFormula (runtimeFormula);
        _parameter.SetValue(intValue);