Radiobutton needs to change text/date range -- need help!

Good day, everyone!

I've been trying to get this to work for a few hours now, and I'm stuck. I tried researching several terms on SDN, but I've not found a message that seems to address what I need. Here's the situation:

I have two radiobuttons, followed by a date field with no interval (single date only). This is the default for radiobutton 1. If radiobutton 2 is selected, I need the description for the date field to change, and now the date field needs to have an interval so the user can enter a range. So, it's like this:

Case 1:

(X) Date1

( ) Date 2

Date1: [ ]

Case 2:

( ) Date1

(X) Date 2

Date2: [ ] to [ ]

I've tried making the Date1/Date2 text a comment to change the text based on the button selected, but I can't figure out how to change the date field itself to accept just one date vs. an interval.

Does anyone have any ideas on how to solve this? As always, points awarded for ALL helpful answers.

Thanks in advance,

Dave