problem with replacing values formatted as "time"

Hi All,

Can you please help me with one issue.
I`m trying to use excel macro to replace some values. The problem is that the values I want to replace are "time" formatted (hh:mm:ss) and the following command fails (actually do nothing):

 Sheets("Sheet1").Select
    Cells.Replace What:="23:37:00", Replacement:="time2sleep", LookAt:=xlPart, _
        SearchOrder:=xlByRows, MatchCase:=False, SearchFormat:=False, _
        ReplaceFormat:=False

But in opposite way it works (replacing "time2sleep" to "23:37:00")

Thank You in advance for answers.