interesting. I guess next to this control you can place a label then check to see if its visible and if not make it visible else hide it.
I guess another method is to make a custom control similar to a tooltip or has the same characteristics as a tool tip then show this in the position of the textbox when you click the textbox or something. It's an interesting one....
I've kind of managed to do it with the tooltip. I simply set it as a global variable then on the click event of the textfield, check to see if its active, if it is then made it unactive and make sure it is not set to ShowAlways otherwise I set the tool tip and make it active and set it to ShowAlways. Seems to work