how to execute workitems or user decisions of workflow from webdynpro application

Hi,

I am working onn webdyn pro and workflow.

in my requirement user can  perform approve or reject from webdyn pro application and from SBWP also.

user can approve or reject from webdyn pro appications using buttons in appications.

i came to know that we can use these FM

1.SAP_WAPI_WORKITEMS_TO_OBJECT

2.SAP_WAPI_GET_DEPENDENT_WIS

3.SAP_WAPI_DECISION_COMPLETE

please tell can we use these function modules or any other  way to acheive these requirement

please tell how to acheive these .

Thanks,

Phani.