Randomize()

This is used to create a seed value for the Rnd() function, this helps vary the output of the random seed.  You would place a number as the seed, one good option is to use the Second(Now()), this would make sure that your seed is different every time you run the script.

Script: 

'Random number between 1 and 100
Sub Main
    Dim random_number As Double
    Randomize(Second(Now())
    random_number = Rnd() * 99
    MsgBox random_number
    MsgBox Int(1 + random_number )
End Sub

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