Connect to the excel file using Tableau. After that, you can create your view and use a parameter to control the values. So when you change a values, Tableau sends query to your excel, performs required calculations, and update your chart.
Few examples for your reference.
Let me if that works or not.
Thank you for you answer
I created a parameter and was able to choose it in the dashboard thanks to your link but in the examples, as far as i understand, use the parameter to calculate data within Tableau. I explicitly need to hand the parameter to Excel and calculate the new data there. For example I set the parameter in Tableau to "1" and in a linked cell in Excel the "1" is exported. That would be already enough for me
Is that possible? Thank you very much!
As of now Tableau doesn't have write back capability. So you won't be able to update your excel data. You can vote for this idea.
If that helps please mark the answer as correct and helpful.