Iteration

Option Compare Text
Function SWITCHES1(strRept As String, rngRept As Range, Optional strDelim As String) As String
Dim lngRept As Long, strY As String
If strDelim = "" Then strDelim = ","
For lngRept = 1 To rngRept.Value Step 1
    If lngRept = 1 Or lngRept = rngRept.Value Then strY = "51 - 52" Else strY = "49 - 51"
    SWITCHES1 = SWITCHES1 & strDelim & Replace(Replace(strRept, "[X]", lngRept), "[Y]", strY)
Next lngRept
SWITCHES1 = Replace(SWITCHES1, strDelim, "", 1, 1)
End Function

B3: =SWITCHES1("GigabitEthernet, [X]/0/[Y]",$A2)

I get the #NAME? error on both B2 and B3 cells