Best way to program dynamic wordpress widget settings?

I am currently developing my first widget plugin for Wordpress, everything is working as I would like although I am a little stumped as to how I can program my back-end widget settings.

At the moment I have the following Options/form fields on the back end widget settings:

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Widget Title
Widget Text
Widget Background Colour
Select Widget Design

Widget Design 1 Options

Widget Design 2 Options
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What I would like is for only one widget design options to be displayed depending on which widget design is selected if that makes sense?

For example if from the main settings 'widget design 1' was selected -> then show widget design 1 options below and don't display widget design 2 options, and so on......

I have tried and failed with some PHP if statements and jQuery but with no luck so was wondering if anyone had a recommendation on how to achieve this best?

Thanks!

via Chebli Mohamed