USING MASKING TEXTBOX

I use sometimes the 'simple' TEXTbox for input due to the need for control
the sofar total input chararter by character.
sample

Private Sub txtnewUser_Change()
trim (txtnewUser.Text)
txtnewUser.Text = UCase(txtnewUser.Text) '  force uppercase
if  txtnewUser.Text ="JACK" then
....  ' do somthing
end if

if instr(txtnewUser.Text) ="!" then
'print not allowed
end  if

End Sub

Entry has to be sometimes left or rigth aligned.
Now here's my problem,
   Continuing typing in box always start e.g. at left if left alligned,
   I want to continue at cursorlocation after last character, because
   now after every character it starts at left position shifting other
  characters to right,  only way is to place cursor every time at right