(SOLVED) How to sum of two or more columns when certain cell meets conditions

Hi,

I try to explain the problem by stating what's in the cells
A1 10 B1 12 C1 12343
A2 13 B2 14 C2 11000
A3 15 B3 24 C3 12343
etc

In cell D1 the invoicenummert is stated.
What I want to achieve is that in cell D2 the sum appears of the digits in column A and B that meets the invoicenumber stated in D1. So when in D1 the nummer 12343 is entered that in cell D2 the results (SUM) gives (10+12+15+24= 61). This example is with two columns. In my sheet I have more and more rows.
I can't seem to find the right formula.
Can anyone help?

Thanks

Hi rvfotopro and welcome to the forum,

In cell D1 put this formula.

=SUMIF(C1:C3,C1,A1:A3)+SUMIF(C1:C3,C1,B1:B3)

Is the invoice number always in column C?

Try this
=SUMPRODUCT((A1:B3)*(C1:C3=L1))

The A1:B3 is the range that contains the numbers. The C1:C3 is the range that contains the Invoice number. L1 contains the Invoice number that you enter manually. Replace these ranges with your own values. You can also replace the fixed ranges with named dynamic ranges to cover the variable data rows and columns.