Deactivate Field in 0006

Hi! Experts,

I have created Hire Actions with group of some infotypes,

Now what is the problem is , when i am hiring my employee, in IT0006 there is one infofiled which is mentions mendatory in standard system, which i want to deactivate or optional(which is not required in my hiring action) , can anybody help me out to make it as i want..

I think i can be soleved in Cutomizing header in IMG but how ...plz explain...

Thanks ...!!! in advance...

Sneha.