You can try:
if ATTR([posting date]) = MAX([posting date])
One possible solution would be to use your calculation, then use window_count to get it aggregated as desired.
Hope this helps!
Thanks for the reply but sadly don't think I can use your suggestion.
I am not quite sure how to use the window_count you mentioned. I read up on it on the knowledge base but its still fuzzy to me. Does it basically mean that I am able to grab a figure from the table in the same row but different column?