Si a alguien le sirve
Option Explicit
Private Declare Function FindWindow Lib "user32" Alias "FindWindowA" (ByVal lpClassName As String, ByVal lpWindowName As String) As Long
Private Declare Function GetClientRect Lib "user32" (ByVal hwnd As Long, lpRect As RECT) As Long
Private Type RECT
Left As Long
Top As Long
Right As Long
Bottom As Long
End Type
Function a()
Dim hwnd As Long
Dim Rectangle As RECT
hwnd& = FindWindow("Shell_TrayWnd", "")
GetClientRect hwnd&, Rectangle
MsgBox "Ancho : " + Str$(Rectangle.Right - Rectangle.Left) + " Pixels." + Chr$(13) + "Alto : " + Str$(Rectangle.Bottom - Rectangle.Top) + " Pixels."
End Function