Option Explicit

Public Declare Function SetTimer Lib "user32" _
(ByVal hWnd As Long, _
ByVal nIDEvent As Long, _
ByVal uElapse As Long, _
ByVal lpTimerFunc As Long) As Long
 
Public Declare Function KillTimer Lib "user32" _
(ByVal hWnd As Long, _
ByVal nIDEvent As Long) As Long

Private m_TimerID As Long
 
Public Sub StartTimer(ByVal Duration As Long)
    If m_TimerID = 0 Then
        If Duration > 0 Then
            m_TimerID = SetTimer(0, 0, Duration, AddressOf TimerEvent)
            If m_TimerID = 0 Then
                MsgBox "Timer initialization failed!"
            End If
        Else
            MsgBox "The duration must be greater than zero."
        End If
    Else
        MsgBox "Timer already started."
    End If
End Sub
 
Public Sub StopTimer()
    If m_TimerID <> 0 Then
        KillTimer 0, m_TimerID
        m_TimerID = 0
    Else
        MsgBox "Timer is not active."
    End If
End Sub
 
Public Property Get TimerIsActive() As Boolean
    TimerIsActive = (m_TimerID <> 0)
End Property
 
Private Sub TimerEvent()
    Debug.Print "Timer event fired: "; Format$(Now, "long time")
    StopTimer 'Comment out if timer should run all the time.
    'Your code here.
End Sub

Option Explicit

Public Declare Function FindWindow Lib "user32" Alias "FindWindowA" (ByVal lpClassName As String, _
                 ByVal lpWindowName As String) As Long
                 
Private Declare Function SendMessage Lib "user32" Alias "SendMessageA" (ByVal hwnd As Long, ByVal wMsg As Long, _
                ByVal wParam As Integer, ByVal lParam As Any) As Long

Private Declare Function FindWindowEx Lib "user32" Alias "FindWindowExA" (ByVal hWndParent As Long, _
                ByVal hwndChildAfter As Long, ByVal lpszClass As String, ByVal lpszWindow As String) As Long

Private Const WM_CLOSE As Long = &H10
Private Const WM_KEYUP As Long = &H101
Private Const WM_KEYDOWN As Long = &H100
Private Const VK_RETURN As Long = &HD
Private Const WM_SETFOCUS As Long = &H7
Private Const WM_ACTIVATE As Long = &H6
Private Const WM_KILLFOCUS As Long = &H8
Private Const WM_SETTEXT As Long = &HC
Private Const WM_CHAR As Long = &H102

Public Sub CheckWindow()

Dim hwnd As Long
Dim hwndex As Long
Dim sName

Do While Not bStop

sName = frmMain.txtAppName.Text

If LenB(sName) <> 0 Then
    hwnd = FindWindow(vbNullString, sName)
    If hwnd <> 0 Then
        hwndex = FindWindowEx(hwnd, 0&, "Edit", "")
        If hwndex <> 0 Then
            'SendMessage hwndex, WM_ACTIVATE, 1&, 0&
            'SendMessage hwndex, WM_SETFOCUS, 0&, 0&
            'SendMessage hwndex, WM_KEYDOWN, VK_RETURN, 1&
            'SendMessage hwndex, WM_KEYUP, VK_RETURN, 1&
            
            'SendMessage hwndex, WM_SETTEXT, 0&, "hello"
            
            SendMessage hwndex, WM_CHAR, 13, 0&
        End If
    End If
End If

DoEvents
Loop

End Sub