strrev("star")

Try this:

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'''''''''''''''Script Starts Here''''''''''''''''''''''''''

Dim i
Dim iStrLen
Dim strOut
Dim strTmp
Dim strMyString

strString=InputBox("Please enter the string to be 
reversed:")
iStrLen = Len(strString)
For i = 0 To Len(strString) - 1
strOut = Mid(strString, iStrLen - i, 1)
strTmp = strTmp & strOut
Next

strMyString = strTmp
msgbox strMyString



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'''''''''''''''Script Ends Here''''''''''''''''''''''''''

Please let me know if it helps

Option Explicit
Dim Str, Cnt , Rstr , i

Str = "Shiva"
Cnt = len(str)

For i = 1 to Cnt
	Rstr = mid(str , i ,1) &Rstr
Next
Msgbox Rstr

Str = InputBox("Please enter the string to be reversed:")
Cnt = len(str)
For i = 1 to Cnt
	Rstr = mid(str , i ,1) &Rstr
Next
Msgbox Rstr

'Code to reverse a string without using strrev using 
functions

Function stringreverse(a)
strlen=len(a)
For i = strlen to 1 step -1
	strrev=mid(a,i,1)
	stn=stn+strrev
Next
	msgbox stn
End function 

Dim strrev,strlen, strname,stn
a=inputbox ("enter the string to reverse")
stringreverse(a)