Using the functional methods with workflows

Hi All,

I'm passing the plant number to a workflow by triggering an event in a user-exit. The workflow uses a functional method of an ABAP class and retrives the plant details. While binding the functional method back to the workflow, the binding includes a partial expression like this..

&_WI_OBJECT_ID.PLANT(W_PLANT=)&

Here, if I give &_WI_OBJECT_ID.PLANT(W_PLANT='1000')& I get no error and the details of plant 1000 are retrived successfully. How do I pass this value dynamically?

Regards

Indu.