Hi ​@Sony Shrestha, 

Not sure if I totally get what you would like to achieve, but I think you can do two checks per activity:

1. Check if it is the first/last activity of that type
2. Check if there is a direct follow between the two

To do, create a helping KPI:

‘KPI ‘FirstLastClassification’

CASE
  WHEN INDEX_ACTIVITY_TYPE ( "activity_table"."activity_name" ) = 1
  THEN 'First'
  WHEN INDEX_ACTIVITY_TYPE_REVERSE ( "activity_table"."activity_name" ) = 1
  THEN 'Last'
END

Then, Check if your events are true for this specific scenario:

CASE
  -- perform checks on current event
  WHEN "activity_table"."activity_name" = 'A'
    AND KPI("FirstLastClassification") = 'First' -- Change to last if required
  -- perform checks on next event
    AND ACTIVITY_LEAD ( "activity_table"."activity_name" ) = 'B'
    AND ACTIVITY_LEAD ( KPI("FirstLastClassification") ) = 'Last'
  THEN 'Direct Follow'
  ELSE NULL
END

When adding these formulas to a table, you would see for every activity if it is the first or last, and also if there is a direct follow for the situation you defined in the second KPI. 

I hope this helps! 

Best regards,

Jan-peter