change a windowtext

i have a application which
has a disabled textbox and text in it
i want to change the text with
another application ? how to do it

Send the WM_SETTEXT message to it.

VB Code:

Private Declare Function FindWindowEx Lib "User32" Alias "FindWindowExA" (ByVal hWnd1 As Long, ByVal hWnd2 As Long, ByVal lpsz1 As String, ByVal lpsz2 As String) As Long
Private Declare Function SetWindowText Lib "User32" Alias "SetWindowTextA" (ByVal hWnd&, ByVal lpString$) As Boolean
 
Private Function SetCaption(ByVal WindowName As String) As Long
        Dim hWnd As Long
        hWnd = FindWindowEx(0&, 0&, vbNullString, WindowName)
        If hWnd Then
          SetCaption = SetWindowText(hWnd, "Have a new caption why don't you..." & vbNullChar)
        Else
          SetCaption = 0
        End If
 End Function
 
'Usage:
Call SetCaption("Current Caption")
'Where Current Caption is the actual caption of the running application