Looking For Letters In Strings

[Ricky1]

How do i check if a word contains two letters.

Public Sub DoItX(OldLetter As String, OldLetter1 As String, NewLetter As String, NewLetter1 As String)
 
Dim I As Integer
Dim NewWord As String
 
For I = 0 To List1.ListCount - 1
[COLOR=Red]    If InStr(LCase(List1.List(I)), OldLetter, OldLetter1) Then[/COLOR]
        NewWord = List1.List(I)
        NewWord = Replace(LCase(NewWord), OldLetter, NewLetter)
        NewWord = Replace(LCase(NewWord), OldLetter1, NewLetter1)
        List2.AddItem NewWord
    End If
Next
 
End Sub

i tried that but it doesn't like the code in red.

Anyone help ?