Hi:
When you register your stored process in the Metadata, using the Stored Process Wizard in EG (or using SAS Management Console) you CAN define a default parameter value, which will be used if there is nothing specified when the stored process is invoked (as when you write a custom app or invoke using the stored process web app.)
As described on this page:
http://support.sas.com/rnd/itech/doc9/dev_guide/stprocess/input.html
Defining Parameters
Most stored process client interfaces allow a client to pass any input parameter. There is no requirement to define parameters before executing the stored process, but there are many advantages to describing parameters in stored process metadata:
--Parameter definitions can specify labels and descriptive text. This information can be used by client interfaces to present a more attractive and informative user interface. Other presentation options include grouping parameters and expert flags.
--Default values can be specified. The default value is used if the parameter value is not specified by the client.
--Default values can optionally be flagged as non-modifiable to allow a fixed parameter value to always be passed into a stored process. This can be useful when using an existing program that accepts many input parameters. You can register a new, simpler stored process that has some fixed value parameters and fewer client specified parameters.
You can also register multiple stored processes for a single program. Each stored process definition can pass in unique fixed parameter values to the executing program to force a particular operation or otherwise affect the execution of the stored process.
You could also control the value for input parameters using macro program logic, such as this:
[pre]
%if &reptype = %then %let reptype = Date;
%if %upcase(&reptype) = DTAE %then %let reptype = Date ;
[/pre]
which is testing for a null value for &REPTYPE and setting the value for Date in the first %IF statement and doing a minor adjustment in the second %IF statement (in case you let them type the parameter value instead of choosing it from a drop down list).
But, macro conditional logic must be contained within a macro program, it is not allowed in "open" code. For more help with macro programs, you should consult the SAS Macro Facility documentation or contact Tech Support.
cynthia