To build on what the previous two posters said, you basically want to use your textbox as a variable.
So in the on_click code of your command button put something like:
Form1.recordsource = "select * from tablename where columname like '" & textbox1.value & "*';"
form1.requery
This will change the underlying record source of your form based on the text in your text box.
You can actually get a nice filter going with several options via combo boxes and list boxes using this technique. I've got a working sample somewhere of about 6 options to filter a query based form somewhere.
Don't forget to check to make sure there is actually a value in the text box first.