Best way to program tooltips in VBA

[MarkSt]

Hi,
I wrote a VBA macro that reads machine downtimes from a database and visualises this information in a calendar.
Each cell in the excel calendar represents a 2 hour shift. When a cel is clicked a tooltip appears with detailed information.
This works fine but performance is bad. Before adding the 'selection.Validation' command the performance was good.
So the problem is this statement.
Are there better ways to do this ?

Code : coloring each cell and defining the tooltip :

                            Range(Cells(iRow, iColumn), Cells(iRow, iColumn)).Select 'Volledige performantie
                            With Selection.Interior
                                .Pattern = lPattern
                                .PatternColorIndex = xlAutomatic
                                .Color = xlNone 'Verwijder kleur
                                .TintAndShade = 0
                                .PatternTintAndShade = 0
                            End With
                            
                            With Selection.Validation
                                .Delete
                                .Add Type:=xlValidateInputOnly, AlertStyle:=xlValidAlertStop, Operator _
                                    :=xlBetween
                                .IgnoreBlank = True
                                .InCellDropdown = True
                                .InputTitle = Worksheets(sSheet).Cells(iRow, 1).Value
                                .ErrorTitle = ""
                                .InputMessage = sComment
                                .ErrorMessage = ""
                                .ShowInput = True
                                .ShowError = True
                            End With