The standard way to do this would be with a combobox. If you haven't already
done so, create a form based on your table or query, including all the
fields you want displayed. Then simply:
Add a combo box to your form. The Combobox Wizard will pop up
Select "Find a record based on the value I selected in my combobox."
From the table or query the form is based on, click on the field you're
searching by (a field that is unique for each record) to move it to the right
side.
Hit Next.
Size the column appropriately.
Hit Next.
Name the combobox.
Hit Finish.
Now you can drop the combobox down and scroll down to the item to search by,
or you can start to enter the item, and the combobox will "autofill" as you
type. Hit <Enter> and the record will be retrieved.
If you insist on using a textbox, do the above, then plug the code Access
generates for the combobox into the AfterUpdate event of the textbox. Just
replace name of the combobox with the textbox name.