'первая прога проверяет ячейки 1 столбца до первой пустой, вторая - все ячейки первого столбца
Код:

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Public Sub TruncCell()
Dim WBK As Workbook
Dim WSHT As Worksheet
Dim i As Integer
Set WBK = Application.ActiveWorkbook
Set WSHT = WBK.ActiveSheet
i = 1
Do While WSHT.Cells(i, 1) <> "" And i <> 65536
WSHT.Cells(i, 1).Value = Left(WSHT.Cells(i, 1).Value, 100)
i = i + 1
Loop
End Sub
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Public Sub TruncCellALL()
Dim WBK As Workbook
Dim WSHT As Worksheet
Dim i As Long
Set WBK = Application.ActiveWorkbook
Set WSHT = WBK.ActiveSheet
For i = 1 To 65536
WSHT.Cells(i, 1).Value = Left(WSHT.Cells(i, 1).Value, 100)
Next i
End Sub