You could try this on a copy of your workbook also.

[VBA]Sub GetSecsBetween()
Dim rRange As Range
Dim rFill As Range
Dim dStop As Double
Dim rCell As Range

Set rRange = Range("A3", Cells(Rows.Count, 1).End(xlUp))
Application.ScreenUpdating = False
For Each rCell In rRange
dStop = rCell(1, 2)
Set rFill = Cells(3, Columns.Count).End(xlToLeft)(1, 2)
rCell.Copy rFill
Range(rFill, Cells(Rows.Count, rFill.Column)).DataSeries _
Rowcol:=xlColumns, Type:=xlLinear, _
Step:=1 / 86400, Stop:=dStop
Next rCell
Cells.Columns.AutoFit
Application.ScreenUpdating = True
End Sub[/VBA]