You could try using the KeyPress events and remove the need for a timer
Code:
Option Explicit

Private Sub Form_Load()
Text1.Text = ""
Text12.Text = ""
End Sub

Private Sub Text1_KeyPress(KeyAscii As Integer)
Text12.Text = Text12.Text & Chr(KeyAscii)
End Sub

Private Sub Text12_KeyPress(KeyAscii As Integer)
Text1.Text = Text1.Text & Chr(KeyAscii)
End Sub