>>>>>>>

>>>>>>>This is just one approach I tried.
>>>>>>>
>>>>>>>     (mm:mmCheckBox ID="chkAgree" runat="server" Checked="false" Text="I Agree to the Terms" /)
>>>>>>>             
>>>>>>>     (mm:mmButton ID="btnAgreeContinue" runat="server" Text="Continue" 
>>>>>>>                Enabled="False" /)
>>>>>>>     
>>>>>>>

>>>I couldn't get this to work. I do see the script is injected when I look in firebug but I also see when I drill down the button ID is a long name starting with ctl00_ctl00_Retirement Management System_cphOuterContent_cphMainContent_RightContent_ctrlAgreement_btnAgreeContinue
>>>
>>>Can that have anything to do with it?
>>
>>Well the string in getElementById() in the script obviously has to match to actual Id of the button in question. Can't you just give the button a specific (short) Id ?
>
>Yep, my button ID is as above, but it doesn't show up that way in firebug. The button is in a Web User Control which is added to a content page that is in a nested master. I would guess it gets altered when it is dynamically added. I do have a routine for getting the id of a control, maybe I need to obtain that in code and alter the code to pass that in.

Sorry, I'd forgotten about that behaviour. I guess, if the checkbox and button are at the same level then this would work in the function:

var s = checkbox.id.substr(0, checkbox.id.lastIndexOf("_") + 1) + "btnAgreeContinue"; ;
var button = document.getElementById(s);
button.disabled = !checkbox.checked;

but there must be something a bit more elegant.....