The problem with parsing is that if someone changes the field settings to reverse the audit entries then the parsing will break. A more robust solution would be to create a pipeline that triggers whenever the Status field changes, and then save the date in a field "Last Status Date".
If you really want to parse it then this should work if your audit entries are always at the top:
Today() - ToDate(Trim(Left(Right([Status], Length([Status]) - Find([Status], "[")), " ")))
Hope that helps!
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Doug Henning
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