you can do something like this:
make the textbox small at start, and then make it larger when user enters data.
Sub txtMsg_TextChanged (Old As String, New As String)
Dim txt As EditText
txt = Sender
doForSizeHint(New, txt)
End Sub
Sub doForSizeHint ( s As String , aTextBox As EditText )
If s.Length = 0 Then
aTextBox.TextSize = 16
Else
aTextBox.TextSize = 32
End If
DoEvents
End Sub