Public Sub ClearA()
Dim i As Long, LR As Long
LR = Range("B" & Rows.Count).End(xlUp).Row
Application.ScreenUpdating = False
For i = 1 To LR
If Range("B" & i).Value = "ABC" Then
Range("A" & i).ClearContents
End If
Next i
Application.ScreenUpdating = True
End Sub