-- sample data

DROP TABLE #Sample

CREATE TABLE #Sample (UserName VARCHAR(15), [Time] CHAR(8), FieldValue TEXT)

INSERT INTO #Sample (UserName, [Time], FieldValue)

SELECT 'Bob Hope', '12:00:00', 'We cannot do anything until 1 O''Clock - the penguin needs defrosting'

UNION ALL SELECT 'Rolf Harris', '13:00:00', 'We cannot do anything until 1 O''Clock - the penguin needs defrosting I have defrosted it'

UNION ALL SELECT 'Jeff Bridges', '13:13:00', 'We cannot do anything until 1 O''Clock - the penguin needs defrosting I have defrosted it It''s Alive!'

UNION ALL SELECT 'Jenny Bond', '13:46:25', 'We cannot do anything until 1 O''Clock - the penguin needs defrosting I have defrosted it It''s Alive! I let it go.'

-- solution

;WITH SequencedData AS (

SELECT

UserName,

[Time],

FieldValue = CAST(FieldValue AS VARCHAR(MAX)),

rn = ROW_NUMBER() OVER (ORDER BY [Time])

FROM #Sample

),

rCTE AS (

SELECT UserName, [Time], rn,

UserString = FieldValue,

FieldValue = FieldValue

FROM SequencedData

WHERE rn = 1

UNION ALL

SELECT tr.UserName, tr.[Time], tr.rn,

UserString = LTRIM(REPLACE(tr.FieldValue,lr.FieldValue,'')),

FieldValue = tr.FieldValue

FROM SequencedData tr

INNER JOIN rCTE lr ON lr.rn+1 = tr.rn

)

SELECT UserName, [Time], UserString

FROM rCTE