@Roland: Thanks for your response, but it is too simple indeed. The current value (20) isn't a 'week-record', but actually the sum of some other field.
I've tried to translate my real problem in some bite-sized Qlikview example. Maybe my example wasn't clear.
Thanks anyway ;-)
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@Halmar: Your values are correct but as mentioned to Roland, the current value isn't week 201145, but a formula on some other field. Maybe your solution can help me anyway. I will try to translate your suggestion back to my real problem.