What should i do for pro site if I have plug in for differend level

Hi, I'm using WHMCS to handle my Pro site payments and registration .

Here are the levels and the abilities I want :
1) Silver-pro
plug in - Formidable form 1,3,5,7

2) Gold - Pro
Plug in -Formidable form 1,2,3,4,5,6,7,8

I have this two levels share with the same plug in ,my concern lies is how to i do for this plug in could assign who is Silver level and Gold level to access by their capabilities ?

I mean when the users who apply be Silver level member, so he must have the specify plug in and content access with Silver level.

Users can upgrade or downgrade their level through WHMCS , and even after upgrade or downgrade is not affected .

For example : If user upgrade from Silver to Gold ,so he can access all the forms and entries ,but when he is downgrade, he is back to Silver level and only can access form 1,3,5,7 .

How to achieve this ? Do i need custom code for this ?

Thanks