# How do I multiply relative time values with previous time steps?

I have this formula:

``````CustomersAdded[t]*CustomerRevenue[0] + CustomersAdded[t-1]*CustomerRevenue[1] + CustomersAdded[t-2]*CustomerRevenue[2]
``````

CustomersAdded is a number, CustomerRevenue is a currency amount and is relative.

The idea is that I have an idea of the number of customers I’ll add per month, and then a projected cash flow for month 1, 2 etc

Is there a way of writing this formula so that I don’t have to repeat the `t` arithmetic? for every month (assuming I want to add more months to this projects cash).

Hi Ben, looks like you want to make use of the Spread function! See forum post here explaining how it works.

For your purposes the formula `spread(CustomersAdded [0:t],CustomerRevenue [0:t])` should achieve your goal!

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I did see the spread function, but didn’t realise it worked like this

What’s the difference between `T` and `t` here?

I’ll give this a shot, thanks @Sanjeev_Sandhar

Apologies - just a typo! No difference! Will amend.

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