Define a different summary field that does not specify the running total option and use it in your Get Summary function call.
You may also be interested in summary reports that use Sub Summary Layout Parts: Creating Filemaker Pro summary reports--Tutorial
This link is to an old, but still relevant tutorial. If you have any comments or questions about it, feel free to post those comments here--comments posted to the tutorial will not pop the thread back up into Recent Items and I thus am unlikely to see that any such comments were posted.
i added a 2nd summary field that does the summary of the hours_spent but what i get now is the total of all different sessions, basically it doesn't group according to the session_kind field. that was the reason why i initially chose to have a running total, cuz then you get a 2nd option to sort according to a different field.
is there a way how to make summary fields depend on each other?
i guess i miss a beginners error somewhere, but where is it :-S
use: GetSummary ( summary_field ; kind_of_session )
Where Summary_Field is the new summary field that does not specify the running total option. Be sure the records you want to summarize are in your found set and sorted by kind_of_session.
Put Summary_field inside a Sub Summary layout part set up to be "when sorted by kind_of_session".
Either way will give you a sub total from the records currently present in your found set if they are also sorted by the kind_of_Session field.
i chose the 1st option, but for some reason i can't choose any summary field in the calculation field as basis for the GetSummary. that was also my intuitive approach but as i couldn't select it in the options i dropped this one.
The calculation field with GetSummary and the Summary field that it references must be defined in the same table.
And this method only works for a layout based on the same table where you defined the summary and calculation fields.
I suggest that you take a look at option 2. It does not need the additional calculation field. Normally, we use that function when we need to use a subtotal in a calculation.