The problem of assigning a validation control to "two" ValidationGroups

[s9213037]

I would like to let users check the input format of a Textbox during
filling the whole form by clicking a button, say checkButton, to
postback to server.
Further, when clicking the "submit button" to submit the total content
to web server, the foramt of input inside the Textbox can be still
validated.

In other words shortly, how could I assign a validation control to
"two" ValidationGroups. In this case, one is checkButton and the
orther is submit button.

Thanks for any reply.
Regards