...
if (#den1 == 0) {
#den2 = 1;
} else if (#den1 == 1) {
#den2 = 2;
} else if (#den1 == 2) {
#den2 = 3;
} else {
#den2 = 0;
}
Functions are defined on the "Variable Dependencies" tab (see image). The standard way to set up functions is: