Dual Band microstrip antenna using capacitive loading

I am designing a dual band microstrip antenna having low frequency ratio(around 1.25-1.4).For that i require to add capacitors into the slots in my patch..By varying the capacitance , I have to check the change in the two frequencies..Please help me regarding-
1.How i can add capacitor on my patch in ie3d...
2. How to specify capacitance value...
any tutorial material will be helpful..
Thanks!

Guys pls help if any1 had encountered similar problem.. I have finished designing the slotted patch now i dont know how to model capacitor in ie3d and put into the slots of the patch..