>If I'm looping through all the controls on a form, is there something I can check to see if it is a "valid" control, in that it can accept entry from the user? I do not want labels, containers, images, etc. I only want things like textboxes, checkboxes, combos, etc. Do they all have some property/method that I can check for?

Don't look for it. If you will even find one, tomorrow you will add some custom thing breaking the rule. Check BaseClass property for bunch of values, i.e.
IF Inlist(Control.BaseClass,'Textbox','Combobox',...)