Store SUM of input values from a repeat

Hi all

I have a repeater which shows on the page a number of rows. Each row has an input field and I’ve given them a name and id like this:

dmx-bind:id="inp_hoursRate[$index]" name="hoursRate[]" type="number"

I want to store the sum of these into a variable and I thought it would be easy but am now struggling to work out how!

Any help or pointers would be very much appreciated.