Here's how I click on a control in another app through code. All you need is the handle.
Code:
'''''''
Private Declare Function SendMessage_Long Lib "user32" Alias "SendMessageA" (ByVal hwnd As Long, ByVal wMsg As Long, ByVal wParam As Long, ByRef LParam As Long) As Long
Private Const WM_LBUTTONDOWN As Long = &H201
Private Const WM_LBUTTONUP As Long = &H202
Private Const WM_KEYUP As Long = &H101
Private Const WM_KEYDOWN As Long = &H100
Private Const VK_SPACE As Long = &H20
''''''''
Public Sub WindowAPI_Click(ByVal hwnd As Long)
Dim retVal As Long
retVal = SendMessage_Long(hwnd, WM_LBUTTONDOWN, 0&, ByVal 0&)
retVal = SendMessage_Long(hwnd, WM_LBUTTONDOWN, 0&, ByVal 0&)
retVal = SendMessage_Long(hwnd, WM_KEYUP, VK_SPACE, ByVal 0&)
retVal = SendMessage_Long(hwnd, WM_LBUTTONUP, 0&, ByVal 0&)
End Sub