how do you add up alternate rows in the same column?

Hi,

Hope this is the right place to post this.

I am trying to add up numbers that appear in the same column but only every 5th row.

Here's an example of what I mean, I have a number in cell A2, A7, A12, A17 etc etc. How do I add these up without deleting all the rows in between. That would take forever as there is over 1000 numbers to add up.

Thanks in advance for any help you can give me.

A