can't edit value of CDF parameters in Edit Object Property form

Hi 

I have a capacitance symbol and I need to edit  the capacitance value of that symbol.  I do "q" to bring up the Edit Object Property form and try to enter the value. 

However, I can't edit any value in that form. What would be the potential problem here ? how I can enable editable for those CDF parameters ? 

thanks 

Nhumai