it has field called Staff_Member

It has field called Cut_Code

in main form I enter Staff member using lookup field

I try to populate Cut_Code from Staff_Member choice by on user input in Staff_Member

but the following code returns error when I try to save saying 

Error at line number : 1 
Variable 'Staff' is not defined

My code is

if (Staff[Staff_Member == input.Staff].count()  <  10000)

{

    

    temp  =  Staff  [Staff_Member == input.Staff];

  

    

    input.Cut_Code = temp.Cut_Code;

   

}

Can you help please.