"Brian" wrote
....
how can I make the data in the C cells blank
if there is no time in the A cell?

Try instead in C1:

=IF(A1="","",IF(A1=1540,0,IF(AND(A11540,A1<2400), A1-1540,A1+820)))

Copy down by a safe, max expected # of rows
to say, C100?
(can copy down ahead of input in col A)
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And if you want an auto-sort on a new sheet,
try this play ..

(Assume the source data above is in Sheet1, cols A to C)

In a new sheet
--------------------
Put in A1:

=IF(ISERROR(MATCH(SMALL(Sheet1!$C:$C,ROW(A1)),Shee t1!$C:$C,0)),"",OFFSET(She
et1!$A$1,MATCH(SMALL(Sheet1!$C:$C,ROW(A1)),Sheet1! $C:$C,0)-1,COLUMN(A1)-1))

Copy across to B1, fill down by as many rows
as was done in col C in Sheet1, viz. down to B100

Format col A as Custom, Type: 0000

Cols A and B will return what's in cols A and B in Sheet1,
auto-sorted in ascending order from start of the shift at 1540
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Rgds
Max
xl 97
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