How to execute a workitem (decision task) directly via an URL ?

[Schwartz, Viveka]

Hello,
I want to execute a specific workitemID automatically via clicking on an URL
in an e-mail sent to me.
(The work item is created in an ordinary R/3 system, not BBP.)
 
The workitem is a decision task (obj.type DECISION, method: PROCESS) and
when I click on the URL I
would like to see exactly the same screen (with buttons etc) as when I am
executing a decision work item
via the GUI for HTML .
 
I got a tips about the service BWWF_WI_DECI, but could not find out how this
works since I could not enter
any wi id in the parameters of the URL..
 
Does anybody have any idea on how the URL should look like for BWWF_WI_DECI
to
execute a decision work item directly through this service.
 
Or is there another way of doing this ?