Thanks to @Njabulo Nsibande who created this how-to thread:    The basic idea is this: Every month has a number: January = 1, February = 2, March = 3 .... December = 12 You decide on a multiplier number, let's say: 2 You decide on a base amount of money: R100 Every month you take the month's number and multiply it by the multiplier and the base Rand amount. The result you save into a savings account.   Example 1:   Multiplier: 1 Base