hWnd := FindWindow( 0,"Second Application")
    
    ? hWnd    // There is a hWnd value.
    
    BringWindowToTop( hWnd )

        .... I want to press TAB Key 3 times.

        .... I want to paste text "12abc"

        .... I want to click a button.

PostMessage( hWnd, WM_CHAR, VK_TAB )

   hWndChildAfter := 0
   lpszClass := "Button"
   lpszWindow := NIL     // -> Title / Caption

   nTo := FindWindowEx(hWnd, hWndChildAfter, lpszClass+Chr(0), lpszWindow)
   IF !EMPTY(nTo)
      SendMessage(nTo, BM_CLICK, 0, 0)
   ENDIF

FUNCTION Test(cText)
LOCAL hWnd, oWnd, nTry:=0, cMyFile, cLink, cText_Esas

    cText_Esas :="Test Button on Dialog"
    cMyFile:="C:\fwh\samples\testbtnz.exe"
    
    SHELLEXECUTE( 0, "open", cMyFile, 0, 0, 1 )
    
    do while nTry<10 .AND. EMPTY(hWnd)
        SysWait(1)
        hWnd := FindWindow( 0, cText_Esas)
        nTry++
    Enddo
    IF EMPTY(hWnd)
        MsgAlert("Cannot find hWnd","Error")
        RETURN
    ENDIF
    
    ? hWnd, nTry

    BringWindowToTop( hWnd )
    SysWait(1)
    
    Ob_MouseMove(hWnd, 100, 100)
    Ob_LButtonDown(hWnd, 100, 100)
    SysWait(.1) 
    Ob_LButtonUp(hWnd, 100, 100)    

RETURN

FUNCTION Ob_MouseMove(hWnd, nYY, nXX)
LOCAL nX, nY, hCtrl, aPos 
  nX = nXX + GetWndRect( hWnd )[ 2 ]
  nY = nYY + GetWndRect( hWnd )[ 1 ]
  SetCursorPos( nX, nY )
  hCtrl = WindowFromPoint( nX, nY )
  LogFile( "TestJava.log", { "MM", nX, nY, hCtrl, GetClassName( hCtrl ) } )
  aPos = ScreenToClient( hCtrl, { nX, nY } )
  PostMessage( hCtrl, WM_MOUSEMOVE, aPos[ 1 ], aPos[ 2 ] )
RETURN

FUNCTION Ob_LButtonDown(hWnd, nYY, nXX)
LOCAL nX, nY, hCtrl, aPos 
  nX = nXX + GetWndRect( hWnd )[ 2 ]
  nY = nYY + GetWndRect( hWnd )[ 1 ]
  SetCursorPos( nX, nY )
  hCtrl = WindowFromPoint( nX, nY )
  LogFile( "TestJava.log", { "MD", nX, nY, hCtrl, GetClassName( hCtrl ) } )
  aPos = ScreenToClient( hCtrl, { nX, nY } )
  PostMessage( hCtrl, WM_LBUTTONDOWN, aPos[ 1 ], aPos[ 2 ] )
RETURN

FUNCTION Ob_LButtonUp(hWnd, nYY, nXX)
LOCAL nX, nY, hCtrl, aPos 
  nX = nXX + GetWndRect( hWnd )[ 2 ]
  nY = nYY + GetWndRect( hWnd )[ 1 ]
  SetCursorPos( nX, nY )
  hCtrl = WindowFromPoint( nX, nY )
  LogFile( "TestJava.log", { "MU", nX, nY, hCtrl, GetClassName( hCtrl ) } )
  aPos = ScreenToClient( hCtrl, { nX, nY } )
  PostMessage( hCtrl, WM_LBUTTONUP, aPos[ 1 ], aPos[ 2 ] )
RETURN

#include 'FIVEWIN.CH'

PROCEDURE Main()
   local oFont, oDlg
   define font oFont name 'MS Sans Serif' size 6,15

   define dialog oDlg from 0,0 to 12,35 font oFont title 'Test Button on Dialog'
   @ 1,3 BUTTON "&Button Test on Dialog" size 100,50 font oFont OF oDlg ACTION MsgInfo("Button Test on Dialog")
   activate dialog oDlg centered

return

import javax.swing.*;

public class Main {

    public static void main(String[] args) {
        // Create font
        Font font = new Font("MS Sans Serif", Font.PLAIN, 15);

        // Create dialog box
        JDialog dialog = new JDialog();
        dialog.setTitle("Test Button on Dialog");
        dialog.setSize(300, 200);
        dialog.setLocationRelativeTo(null);
        dialog.setDefaultCloseOperation(WindowConstants.DISPOSE_ON_CLOSE);

        // Create button
        JButton button = new JButton("&Button Test on Dialog");
        button.setFont(font);
        button.setSize(100, 50);
        button.addActionListener(e -> JOptionPane.showMessageDialog(dialog, "Button Test on Dialog"));

        // Add button to dialog box
        dialog.add(button);

        // Display dialog box
        dialog.setVisible(true);
    }
}