Don't listen to Mart ;\)
Here's some code:
 Code:
Function InputBox($strPrompt, Optional $strTitle, $strDefaultValue)
  Dim $objSC
  $objSC = CreateObject("ScriptControl")
  $objSC.Language = "VBScript"
  $InputBox = $objSC.Eval('InputBox("'+$strPrompt+'","'+$strTitle+'","'+$strDefaultValue+'")')
EndFunction

$=InputBox("Enter your input","This is a title")
? "You've put in: "+$