Separate 4 columns of data into 2 cumulative bars

Hi all,

I think the title says all. I want to make a bar chart with 2 cumulative bars out of 4 columns of data. Hence, bar 1 represents the cumulative value of column 1 and 2, while bar 2 represents the data of column 3 and 4. How can I do this?

For clarification purposes I added an Excel document. I want to compare the product 1 + product 2 bar with the product 1* + product 2* bar. Hope this helps.

Regards!