Spool to a file when using bind variables

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Oracle

I am trying to create pl/sql script which will spool the output to a file. The catch is my script is also making use of bind variables and the spooled output is always 0 bytes

Here's my query:

T sqlformat csv
spool c:\users\99387\testspool.txt;
variable End_date varchar2(25);
variable START_Date varchar2(25);
with 

-- Standard_Presets         ------------------------------------------------------------------------------------ START
     Standard_Presets As (
                     Select
                              1                                          HANDLE
                             , Epic_Util.Efn_Din(:START_Date)           START_Date    -- SQL Dev
                              , Epic_Util.Efn_Din(:End_Date) + .99999    End_Date      -- SQL Dev
                     From Dual
                   )
-- Standard_Presets         ------------------------------------------------------------------------------------ end
select START_Date, End_Date   from Standard_Presets;
spool off;

What I have tried:

I have tried running this using using the run statement which prompts me for the Bind Variable values but I get to data in the outfile.
When I run this as a script, I lose the Enter Bind prompts and the spooled file also loses the bind variable values.