Excel Cell Flashing

Assuming you want A1 cell to Flash, you can use below vba and run Flash_Cells:

Sub Flash_Cells()
    Dim xColor As Integer
    Dim xCount As Integer
    Dim xSpeed As Double
    Dim xStart As Double
    Dim xDelay As Double
    Dim xRg As Range
    Dim xTxt As String
    Dim xCell As Range
    On Error Resume Next
    If ActiveWindow.RangeSelection.Count > 1 Then
      xTxt = ActiveWindow.RangeSelection.AddressLocal
    Else
      xTxt = ActiveSheet.UsedRange.AddressLocal
    End If
    Set xRg = ActiveSheet.Range("A1")
    If xRg Is Nothing Then Exit Sub
    For Each xCell In xRg
        If xCell.Value > 4 Then
            xSpeed = 0.6
            Do Until xCount = 6 'Change the time here, how long you want it to flash
                DoEvents
                xStart = Timer
                xDelay = xStart + xSpeed
                Do Until Timer > xDelay
                    DoEvents
                    xRg.Font.Color = vbRed
                Loop
                xStart = Timer
                xDelay = xStart + xSpeed
                Do Until Timer > xDelay
                    DoEvents
                    xRg.Font.Color = vbBlack
                Loop
                xCount = xCount + 1
            Loop
        End If
    Next
End Sub

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If you want to change the period, change this line:
Do Until xCount = 6 'Change the time here, how long you want it to flash

**eenookami**: Code above was sourced from: https://www.extendoffice.com/documents/excel/3676-excel-make-cell-flash.html#a1
Flashing-Cell.xlsm