Evaluate sumproduct function with range variable

Hi,

I have recently started to use Evaluate function so I'm not quite familiar with how it works. I managed to get this code working:

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However, I'd like to change range address text in this function and use additional variables instead of them. It could look something like this, but I can't managed to get it working:

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Do you have any ideas?

Considering that no one could help on this case, as usually I solved this by myself. Here is the solution (in this example StartRow, StartCol, and HowMany variables' values are set in advance, I don't give their value in this case):

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Important thing to consider: if in chosen range Rng3 are any non numeric values, then evaluate formula returns an error. In my case there were column names in the first row, so I needed to include StartRow variable, which is equal to the next row number below column names row (so that only numeric values would be included in a range).