Bom espero que isso te ajude, BlockInput:
http://msdn.microsoft.com/en-us/library/ms646290
Segue abaixo um exemplo:
Declare Function BlockInput Lib "User32" (ByVal fBlockIt As Boolean) As Boolean
'Bloqueia teclado e mouse
BlockInput(True)
'Desbloqueia teclado e mouse
BlockInput(False)
Exemplo completo:
Imports System.Windows.Forms
Public Class WinControl
'This is the function used in order to block the keyboard and mouse:
Declare Function BlockInput Lib "User32" (ByVal fBlockIt As Boolean) As Boolean
'This function will block the keyboard and mouse untill a window with
'the specify caption will appear or the given time in seconds has
'past ( 0 seconds - wait forever).
'If the window with the caption appears than the given key is send
'to it and the input block is removed.
Public Shared Function Wait2Send(ByVal caption As String, ByVal keys As String, ByVal seconds As Integer)
'Indicates if the window with the given caption was found
Dim success As Boolean = False
'Start time of the function
Dim now As DateTime = DateTime.Now
'Begining of keyboard and mouse block
BlockInput(True)
While (success = False And (DateTime.Now.Subtract(now).Seconds < seconds Or seconds = 0))
Try
'Activating the window with desired function
'if the window is not found an exception is thrown.
AppActivate(caption)
'Sending desired key stroke to the application window
SendKeys.SendWait(keys)
'Indicates the window was found and keys sent
success = True
Catch
'Assuming window was not found and sleep for 100 miliseconds
System.Threading.Thread.Sleep(100)
End Try
End While
'Release the keyboard block
BlockInput(False)
End Function
End Class
http://www.codeproject.com/KB/vb/LockKeyboard.aspx
