Is this what you mean?
WITH pass1
AS (
-- First number the ActionTypes giving priority to HELLO lines
SELECT *
, ROW_NUMBER() OVER (PARTITION BY AccountNum, ActionType ORDER BY ISNULL(NULLIF(ActionType,'HELLO'),'') ,DataAction) AS n1
FROM ActionDetails
)
, pass2
AS (
-- Next number the intermediate actions using the newly numbered HELLO actions to partition the data
SELECT *
, ROW_NUMBER() OVER (
PARTITION BY AccountNum
, n1 ORDER BY DataAction
) AS n2
FROM pass1
)
SELECT AccountNum
, DataAction
, ActionType
, CASE ActionType
WHEN 'HELLO'
THEN n1
ELSE NULL
END AS ActionStart
, convert(VARCHAR, n1) + CONVERT(VARCHAR, n2) AS ActionCounter
FROM pass2
ORDER BY AccountNum
, DataAction
MM
select geometry::STGeomFromWKB(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