Do you mean to say "NOT blank" for that first condition?If cell in column B is blank then copy and paste it to column A
Sub MyMacro()
Dim lastRow As Long
Dim myRow As Long
Application.ScreenUpdating = False
' Find last row with data in column A
lastRow = Cells(Rows.Count, "A").End(xlUp).Row
' Loop through all rows
For myRow = 1 To lastRow
If Cells(myRow, "B") = "" Then Cells(myRow, "A").ClearContents
Next myRow
Application.ScreenUpdating = True
End Sub