I'm just learning VB 6 and I don't know what is wrong, it's working, but not for all values I put in (e.g."tt" or "rr") Thank you

Option Explicit

Private Sub calcFee_Click()
Dim intRez, intMsg As Integer
intRez = 1
Dim strCode As String
Const conButton As String = vbOKOnly + vbInformation + vbDefaultButton1 + vbApplicationModal

strCode = txtCode.Text

Select Case intRez
Case Is = StrComp(strCode, "TC", vbTextCompare)
lblFee.Caption = "The fee is " & "$" & 50
Case Is = StrComp(strCode, "RV", vbTextCompare)
lblFee.Caption = "the fee is " & "$" & 15
Case Is = StrComp(strCode, "OS", vbTextCompare)
lblFee.Caption = "the fee is " & "$" & 5
Case Else
intMsg = MsgBox("Invalid Entry! Try again!", conButton, "List Procedure")
txtCode.SetFocus
txtCode.SelStart = 0
txtCode.SelLength = 2

End Select

End Sub