C# - Change Image Inside Of CSS Of Usercontrol?

there's a label control on my master page..if its value is "Value1" ,I want this CSS Sprite to display on my webform..if the Value is "Value2"..the CSS sprite should use some different image..just the image needs to be changed ..nothing else in that Sprite..

I found out that I can use "FindControl" method to find out what value that Label Control of Master Page's currently got..

Now how do I change that image on the banner ?? How do I go about it ? Also that CSS Sprite now is a user control named "myBanner.ascx"(earlier was an aspx file)..Now do I need to make 2 diff usercontrols or I can implement some logic in one usercontrol itself ?

Should I make 2 copies of this "myBanner.ascx" with JUST the "image name" changed in its CSS ???

Hope its not confusing..Actually I am lost :/

What I want is ONE banner which has been made using CSS Sprite ..Now if the "Label Control's "value in the master page is "Value1" then the image to be used on that banner is "IMAGE1" else if "Label Control's" value is "Value2" then "IMAGE2" should be used in that sprite..