How to use two versions of AjaxToolkit in the same project?

Hi all,

   I am using AjaxToolKit 3.0.30512 in my application(.Net 3.5), i am looking to use ATC 3.0.305123 ,why beacauseAsycFileUpload Control is available in this version. When i am trying to add reference for new DLL, it is asking for replace. Is there any possibility to use both DLL's in ths same application? please help!

Thanks in advance,

Reagards,

Srinivas