Forms :: How To Ensure That Textbox Value Displayed Is Based On Combobox Selection

I am designing a Web Database with a bound form to a submit table.

On the form, I have a combo box with selections that should influence the value to be displayed in a textbox also on same form.

For instance the combo box for Staff Name contains list of all Staff and I want the textbox to automatically display the level of the staff that was just selected in the combobox.

I know how to get this done using a combobox but my boss insists that the level should be automatically displayed in the textbox once combobox selection is done.

Using the combobox for level, I used the select statement in the RowSource property :

SELECT Staff_List.Level, Staff_List.Staff_Name FROM Staff_List WHERE (((Staff_List.Staff_Name)=[forms]![frmtest]![cboStaffName]));

I am in a dilemma of how to replicate this for the textbox because textbox only has control source and no RowSource where I can put this select statement.

Also, I will still need to bind this textbox to the submit table with the column name "TxtLevel" in the control source

Please see attached sample access db.

Also note that I cannot use action queries or VBA because it is a Web database and not a client database.