immediate filtering

Hi,

I would like that my subform is immediately filtered as soon as one types a
letter in an unbound searchbox in the form.
If one types an 's' the content of the subform shows only records starting
with s
If one continues with 'e' the subform would show the ones starting with se.
If one would correct that to 'e' by going back and removing the 's' the
records would start with an e.

Any suggestions?

Thanks in advance

Michiel