Concatenate a field in a SQL statment

Is there a way to concatenate a field in a SQL statment, in a Stored Procedure, and use the the alias some place else in the same stored procedure.  In the below, I know that I can't use 'Amount_Paying', I must use another case statment.  Is there a way around using a 2nd case statement.  I know I can create a temp table, but I would like to just refer to the alias in the same SQL statment.

Thanks in advance for any help
LJG


SELECT  tbl_za_Deposit_Start.Deposit_Number,
     Amount_Paying =
        Case
                          When tbl_za_Deposit_Start.Amount_Partial_Paying>0 then 0            
                         else tbl_za_Deposit_Start.Amount_Owed + tbl_za_Deposit_Start.New_Adjustment
                     end,      

                  Amount_Paying + tbl_za_Deposit_Start.P_Pay AS Tot

     FROM tbl_za_Deposit_Start
     WHERE tbl_za_Deposit_Start.Paying = 1