How come I couldn't assign the field with a textbox?

eg.
datADO.Recordset!code = txtCode

I have to use the CStr(txtCode) in order to save into the code.

But another problem is, I want to save a list in a combo box into the DB. I tried using CStr and without, it also have the same problem as my early problem without using CStr.

I tried.
datADO.Recordset!code = cboCode.List(cboCode.ListIndex)
and
datADO.Recordset!code=CStr(cboCode.List(cboCOde.ListIndex)

Both failed.

Plz help. Thx.