Inserting a string into an existing string

[computergroove]

$NewCustomerID = StringReplace($chars, 553, $CustomerID) ;Repaces the Customer ID in tiapp.xml
    $NewCustomerData = StringReplace($NewCustomerID, 562, $CustomerPin) ;NewCustomerData hold the properly modified xml data
    FileOpen("tiapp.xml", 2)
    FileWrite("tiapp.xml", $NewCustomerData)
    FileClose($xmlfile)
    Exit

I am not sure if showing you my code will do anything for my question but here it is anyway. What I can do with the above code is replace a string character for character starting from a certain string. What I want to do is instead of replace the string, I want to insert a string (so the characters after the string insert will move to the right and I wont lose any information). I can't see anything in the string family of functions. Is there something like StringInsert?

[AdmiralAlkex]

There is _StringInsert()