Sub NoScreenFlicker()
'This will add string values to columns A and B without screen flicker
    Dim rCellValue As Range
    Dim rCellValue2 As Range
    Application.ScreenUpdating = False
        For Each rCellValue In Range("A1:A10000")
            rCellValue.Select
            rCellValue.Value = "Add Value Here"
        Next rCellValue
        For Each rCellValue2 In Range("B1:B10000")
            rCellValue2.Select
            rCellValue2.Value = "Add Value 2 Here"
        Next rCellValue2
    Application.ScreenUpdating = True
End Sub