Excel VBA - loop insert rows

Hi, I am very much new to VBA having been on a course last month.
I have a sheet of continuous data and I am trying to create a loop that inserts an empty row every time the text in column A changes. The loop should then move down and continue through until the last line of data.
The logic I used is that it looks to the cell above the active cell to see if if the value is different. If it is it inserts a row above the active cell and then moves down two rows; if it isn't it moves down one. This continues until the active cell reaches a blank cell.
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'loop down column A until cell below <> value above it. then insert new row

Sheets("Rejected Time").Select
Range("A3").Select

Do Until ActiveCell.Value = ""

If ActiveCell.Value <> ActiveCell.Offset(-1, 0).Value Then

ActiveCell.EntireRow.Insert shift:=xlUp
ActiveCell.Offset(2, 0).Select

Else: ActiveCell.Offset(1, 0).Select

End If

Loop

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It does appear to work however I often get an error message stating that I have run out of memory. I think this may be because it is looping through the whole sheet rather than just through the data, and possibly this is because the positioning of the active cell may be incorrect?
I used a processs of trial an error in offsetting the active cell until it worked as it got quite confusing!

Many thanks, and please feel free to question in case I have missed anything out.

Jason