How can I add animation attribute CollapsiblePanelExtender in code-behind aspx.vb

Hi Friends, 

Please help me sort out this issue, how can I add smooth animation attribute in code-behind aspx.vb, ref my below-mentioned code, share your idea and code.

This is my code, getting err. 

Dim cpe_s1 As AjaxControlToolkit.CollapsiblePanelExtender = Cpe_Stage1
cpe_s1.Attributes.Add("onload", cpe_s1.ClientID & "._animation._fps = 30;")
cpe_s1.Attributes.Add("onload", cpe_s1.ClientID & "._animation._duration = 0.5;")

thanks in advance.