Filter menu items based upon item selected from previous field
I have a scenario in agent desktop that I need to recreate on customer portal with regards to menu items in one custom field filtering menu items in a second custom field.
In agent desktop we can easily build the workspace to select "option a" in "custom menu field 1" which will filter "customer menu field 2" to only show options "x", "y" and "z" using workspace rules/triggers. If "option b" is chosen in "custom menu field 1" then we can filter "custom menu field 2" to show items "u", "v" and "w" instead.
Why is there not a standard widget that replicates this functionality in Customer Portal (or have I completely missed the widget that does this)?