I am using this code that I found on the web:

Const PRINTER_ENUM_CONNECTIONS = &H4
Const PRINTER_ENUM_LOCAL = &H2

Private Declare Function EnumPrinters Lib "winspool.drv" Alias "EnumPrintersA" _
        (ByVal flags As Long, ByVal name As String, ByVal Level As Long, _
        pPrinterEnum As Long, ByVal cdBuf As Long, pcbNeeded As Long, _
        pcReturned As Long) As Long

Private Declare Function PtrToStr Lib "kernel32" Alias "lstrcpyA" _
        (ByVal RetVal As String, ByVal Ptr As Long) As Long

Private Declare Function StrLen Lib "kernel32" Alias "lstrlenA" _
       (ByVal Ptr As Long) As Long

-----------------
Public Function ListPrinters() As Variant

Dim bSuccess As Boolean
Dim iBufferRequired As Long
Dim iBufferSize As Long
Dim iBuffer() As Long
Dim iEntries As Long
Dim iIndex As Long
Dim strPrinterName As String
Dim iDummy As Long
Dim iDriverBuffer() As Long
Dim StrPrinters() As String

iBufferSize = 3072

ReDim iBuffer((iBufferSize \ 4) - 1) As Long

'EnumPrinters will return a value False if the buffer is not big enough
bSuccess = EnumPrinters(PRINTER_ENUM_CONNECTIONS Or _
        PRINTER_ENUM_LOCAL, vbNullString, _
        1, iBuffer(0), iBufferSize, iBufferRequired, iEntries)

If Not bSuccess Then
    If iBufferRequired > iBufferSize Then
        iBufferSize = iBufferRequired
        Debug.Print "iBuffer too small. Trying again with "; _
        iBufferSize & " bytes."
        ReDim iBuffer(iBufferSize \ 4) As Long
    End If
    'Try again with new buffer
    bSuccess = EnumPrinters(PRINTER_ENUM_CONNECTIONS Or _
            PRINTER_ENUM_LOCAL, vbNullString, _
            1, iBuffer(0), iBufferSize, iBufferRequired, iEntries)
End If

If Not bSuccess Then
    'Enumprinters returned False
    MsgBox "Error enumerating printers."
    Exit Function
Else
    'Enumprinters returned True, use found printers to fill the array
    ReDim StrPrinters(iEntries - 1)
    For iIndex = 0 To iEntries - 1
        'Get the printername
        strPrinterName = Space$(StrLen(iBuffer(iIndex * 4 + 2)))
        iDummy = PtrToStr(strPrinterName, iBuffer(iIndex * 4 + 2))
        StrPrinters(iIndex) = strPrinterName
    Next iIndex
End If

ListPrinters = StrPrinters

End Function
  
----------------
Public Function IsBounded(vArray As Variant) As Boolean

    'If the variant passed to this function is an array, the function will return True;
    'otherwise it will return False
    On Error Resume Next
    IsBounded = IsNumeric(UBound(vArray))

End Function

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And this is the code I am using to populate the combo box
Private Sub userForm_Initialize()

Dim StrPrinters As Variant, x As Long

StrPrinters = ListPrinters

'Fist check whether the array is filled with anything, by calling another function, IsBounded.
If IsBounded(StrPrinters) Then
    For x = LBound(StrPrinters) To UBound(StrPrinters)
        printer.AddItem StrPrinters(x)
    Next x
    printer.Value = StrPrinters(1)
Else
    Debug.Print "No printers found"
End If

End Sub