Hi @feuerbach thanks for your query. I am afraid that the feature to have a custom keypress dependent on screen location is not something we have within the standard Tobii Core Software as included with the Tobii Tech range of eye trackers (4C, EyeX)
However, I think you will find most useful the third party application “Project IRIS” which you can read more about @
http://www.xcessity.at/products_iris.php
It appears this software has the features you are looking for. Please let us know if we can be of any further assistance.