It seems that your variable poplc is a struct. In order to mulitply its values you need to access the fields of the struct.
I try to explain it in a mini example.
a.value = 1;
b.xyz = 2;
Try to multiply a and b
c = a*b
You will get the error: "Undefined operator '*' for input arguments of type 'struct'."
But if you use
c = a.value * b.xyz
you should be fine.
