David,
It depends on whether this form is in Single view or Continuous view.
If it's in Single view, you can use VBA procedures on the form's Current
event, and the After Update event of the "another text field", to toggle
the Visible property of the other controls. Something like this...
Me.MyTextbox.Visible = Me.AnotherField = "fred"
However, if it's a Continuous form, this is not so easy, as this sort of
code will apply to all records. However, you can use Conditional
Formatting applied to the textbox so the ForeColor and BackColor are
both set to the same as the BackColor of the form... not really
Invisible, but you can't see it
This cannot be done with Command
Buttons.