How to sum without counting N/A or text

Here I am again, seems to be my lifeline recently.

So

Column J, I Want to Deduct I and H, But if there is an N/A in there don't sum it.

This reports back to another main sheet the value in the those tabs on tab 2, this is a visual tracker, sheet one is for invoice purposes.

When I type N/A i.e the cable has not been coiled I get the #Value, I assume this is a sumif(s) formula

the formula now is just a basic =sum(H1-I1)

Many thanks
Shane

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