First I disable the button during Page rendering by changing its template to Button Disabled.
My initial plan was to enable/disable the button when the comment item changes. Unfortnatly the change will be only recognized when I leave the item. So I decided to enable the button whenever the comment item gets the focus.
To be able to enable the button I have to give assign an Id. In this case P4_SAVE_BUTTON. The only thing left to do is to define a dynamic action without condition on the Get Focus event of the P4_RUN_COMMENT item and a true action with this code:
For now I'm done with this application, so you will find the final version here. If you have any ideas to improve this application (new functionality or coding), please let me know.