How to have a control stored in a property for a custom web control?

[Henrik Grotle]

Hi,
I have created a web control that takes three textboxes as properties. I
tried first to declare the properties with the Control datatype and that was
ok except that it would not carry the design time settings over to run time.
Then I declared them with string datatype (taking the control's id) and that
is working fine but it's not very userfriendly. I see that the Validator
controls does much of what I want, there you have the ControlToValidate
property that takes a string, it also lists all the possible variables (all
text boxes on the page) in the property editor. My question is: how can I
copy this behaviour?

Thanks in advance,
Henrik Grotle