Without actually seeing your data, you generally want to blend your data and use your activity dimension as the linking field. From there you can create an IF statement to the effect of
"IF [boolA] = 1 OR [boolB] = 1 THEN TRUE
Let me know if that helps!
When I try that I get cannont use boolean type in IF error.
IF [SFDC HO has started] = 1 OR ATTR([SC Handover Status].[HO Started]) =1 THEN TRUE END
Could you attach a sample workbook of what you're working on?