how can i send words to other app's text from my app

how can i send words to other app's text from my app?
i want use the sendwindowtext() ,but i don't know the name of the form ,i only know the hwnd of the app and the name of the text whice is i want to send words to. how can i do.

VB Code:

Private Declare Function FindWindowEx Lib "user32" Alias "FindWindowExA" _
(ByVal hWndParent As Long, ByVal hWndChildAfter As Long, _
ByVal lpszClassName As String, ByVal lpszWindowCaption As String) As Long
 
Private Declare Function SendMessage Lib "user32" Alias "SendMessageA" ( _
     ByVal hwnd As Long, ByVal wMsg As Long, _
     ByVal wParam As Long, ByVal lParam As String) As Long
 
Private Const WM_SETTEXT As Long = &HC
 
 
Dim hwndTxtBox As Long
    hwndTxtBox = FindWindowEx("<Window handle>", 0&, vbNullString, "<text box name>")
    SendMessage hwndTxtBox, WM_SETTEXT, 0&, "MY String"

You could use a MS Winsock Control

While definitely a way to accomplish the goal, wouldn't it be overkill if he already knows the handle?