max = 100000 'we use 1 minute and 40 seconds as a limit on which the script will randomly start
min = 1000 'the script will start after 1 second and randomly start the Error within 1 minute and 40 seconds
'as you will understand these numbers are customizable
Do
Randomize
WScript.Sleep (Int((max-min+1)*Rnd+min))
MsgBox "", 48 + 4096, "Error"
Loop