Problem with Select SIMILAR by script

I create this script button

@script vbscript Option Explicit Function OnClick(ByRef ClickData) If ClickData.Func.sourcetab.selected_dirs.count > 0 Then ClickData.Func.command.RunCommand "Select ALLDIRS" ClickData.Func.command.RunCommand "Select SIMILAR" End Function

I don't understand why the currently selected files are unselected ?

@script vbscript Option Explicit Function OnClick(ByRef ClickData) ClickData.Func.command.deselect = False ' Prevent automatic deselection If ClickData.Func.sourcetab.selected_dirs.count > 0 Then ClickData.Func.command.RunCommand "Select ALLDIRS" ClickData.Func.command.RunCommand "Select SIMILAR" End Function