The ScrollDuration of the RadRotator can be configured through the client method get_scrollDuration, as you correctly guessed. You can get the new value on the client directly from the text box without storing it in a hidden field. Please make sure that you parse the string from the text box with the method parseInt, before passing it to get_scrollDuration. For your convenience I have attached an example of the suggested approach, which you can use as a reference.
I hope that helps.
Best wishes,
Slav
the Telerik team
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