text box cursor setting

Question

i have created a virtual keyboard with a multiline texbox.while typing using my virtual the cursor disappears.How will i get the cursor at the end of the text i enter.

and also,i need the code for backspace button.

txtticket.Text = txtticket.Text.Substring(0, txtticket.Text.Length - 1);

 i have tried this code but it does not clear the text where the cursor  currently points.. 

 

 

 

plz help