category on alphnumeric dimension

[Mahamed_Qlik]

Hi 

I have field named as " Customer_Number"

Cutomer_Number

W4000

W4100

W4300

W5000

W5500

I want to create category as below:
 if( Customer_Number)<4000,'Big',

  if( (Customer_Number)>=4000 and (Customer_Number)<5000,'Medium',

    if( (Customer_Number)>=5000 ,'Small','Others'))) As CustomerCategory;

kindly help;

[Or]

Right(Customer_Number,4) should work, or you could just use use Mid(Customer_Number,2,1) and check if it's <4, exactly 4, or >4.