Broken VBA Loop - vba

Question

I'm sure this is simple I just can't find anything on the Web.
I'm writing a Macro to format XL spreadsheets that i download from a 3rd party application. They come formatted all wacky so i'm trying to make it easier to get the data we need from them.
This is a simple VBA Do Loop that causes the cells in Column BL to update. The data in these cells contain line breaks which don't show up until you double click in the cell. The VBA below causes an update to the cells which achieves the same effect, just with less work. However it is currently crashing excel and I can't figure out why. It works in a single instance, but when I loop -- BOOM!!! -- frozen. Any help would be gently appreciated.
Sub updateCell()
Dim currentValue As String
ActiveSheet.Range("BL1").Select
Do Until ActiveCell.Value = ""
ActiveCell.Offset(1, 0).Select
currentValue = ActiveCell().Value
ActiveCell().Value = currentValue & ""
Loop
End Sub

Answer 1

Try something a bit more direct:
With ActiveSheet
lrow = .Range("BL" & .Rows.Count).End(xlUp).Row '~~> find last row on BL
With .Range("BL1:BL" & lrow) '~~> work on the target range
.Value = .Value '~~> assign its current value to it
End With
End With
Above code is like manually pressing F2 then pressing Enter.
Edit1: Explanation on getting the last row
ActiveSheet.Rows.Count '~~> Returns the number of rows in a sheet which is 1048576
MsgBox ActiveSheet.Rows.Count '~~> run this to confirm
So this line actually concatenates BL to 1048576.
.Range("BL" & .Rows.Count) '~~> Count is a property of the Rows Collection
Same as:
.Range("BL" & 1048576)
And same as:
.Range("BL1048576")
Then to get to the last row, we use Range Object End Method.
.Range("BL" & .Rows.Count).End(xlUp)
So basically, above code go to Cell BL1048576 then like manually pressing Ctrl+Arrow Up.
To return the actual row number of the range, we use the Range Object Row property.
lrow = .Range("BL" & .Rows.Count).End(xlUp).Row
See here more about With Statement.
It has the same effect (with your code) without the loop. HTH
But if what you want is to remove Line Breaks produced by Alt+Enter on a cell, try below:
Dim lrow As Long, c As Range
With ActiveSheet
lrow = .Range("BL" & .Rows.Count).End(xlUp).Row
For Each c In .Range("BL1:BL" & lrow)
c.Value = Replace(c.Value, Chr(10), "")
Next
End With
Where Chr(10) is the equivalent of Line Break replaced with "" using Replace Function.