something wrong with sendmessage API - vb.net

Question

i try to make automatic key presser that make minimized game client do order for me while i work in other thing (aion game client) but nothing work here is the code i use please tell me what is wrong with it
Const WM_SETTEXT As Long = &HC
Const GW_CHILD As Long = 5
Declare Function GetWindow Lib "user32.dll" (ByVal hWnd As IntPtr, ByVal uCmd As Integer) As IntPtr
Declare Function FindWindow Lib "user32.dll" Alias "FindWindowA" (ByVal lpClassName As String, ByVal lpWindowName As String) As IntPtr 'Int32
Declare Function SendMessage Lib "user32.dll" Alias "SendMessageA" ( _
ByVal hWnd As IntPtr, _
ByVal wMsg As Int32, _
ByVal wParam As Int32, _
ByVal lParam As String) As Int32
Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
Dim hWnd1 As IntPtr = FindWindow("AIONClientWndClass1.0", "AION Client")
Dim hWndR2 As IntPtr = GetWindow(hWnd1, GW_CHILD)
SendMessage(hWndR2, WM_SETTEXT, 0, "h")
End Sub
this is the code i use it must show window in the game when i click button1 , but nothing happen
i use visual studio 2013 and windows 10 64 bit

Answer 1

here is my wrong
1st my app need to run as administrator
2nd have to set target cpu to 86x
3rd i fixed my code , and here it is
Const WM_SETTEXT As Long = &HC
Const GW_CHILD = 5
Const WM_KEYDOWN As Integer = &H100
Const WM_KEYUP As Integer = &H101
Declare Function GetWindow Lib "user32.dll" (ByVal hWnd As IntPtr, ByVal uCmd As Integer) As IntPtr
Declare Function FindWindow Lib "user32.dll" Alias "FindWindowA" (ByVal lpClassName As String, ByVal lpWindowName As String) As IntPtr 'Int32
Declare Function SendMessage Lib "user32.dll" Alias "SendMessageA" (ByVal hWnd As IntPtr,ByVal wMsg As Int32,ByVal wParam As Int32,ByVal lParam As IntPtr) As IntPtr
Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
Dim _hndl As IntPtr = FindWindow("AIONClientWndClass1.0", "AION Client")
SendMessage(_hndl, WM_KEYDOWN, &H55, 0)
End Sub
&H55 is virtual key code = u