Hi Kavita,
Although in the requirement, no I/P is required or used still you can create a factor=1(example) operand as an input(this I/P will be working as dummy in that zvariant) and then in that zvariant you can put the required logic to calculate the new factor value which is to be determined as an O/P operand to be used in subsequent rate steps.
Hope it helps.
Thanks,
Rakesh