InStrRev

Return the position of the first occurrence of one string within another, from the end of string.

Syntax 
      InStrRev(string1, string2 [,start][, compare])

Key
   string1        The initial string of Text
   string2        The text we want to find in String1
   Start          Character position in string1 at which to start the search
   Compare        Either vbBinaryCompare or VBTextCompare

Example

result = InStrRev("A B A B", "A", 6)
WScript.Echo result

“Who looks outside, dreams; who looks inside, awakes” ~ Carl Gustav Jung

Related:

InStr - Find one string within another
Replace - Find and replace text
Equivalent in PowerShell: $result = $myvar.lastindexofany("A")