As far as I understand you want to determine the RadToolTip's title value server-side and then set it on the proper tooltip. If my assumptions are correct I suggest to upgrade to our "Futures" build because there are significant improvements in the RadToolTip's implementation. One of them is that a new overloaded method when adding target controls to the RadToolTipManager is available and it takes one additional parameter called value.
I suggest using it for passing the title's value. In case you experience problems in implementation, please open a new support ticket and send us what you have done so far with a detailed explanation of the desired behavior. Once we receive it we will do our best to help you.
the Telerik team