Hi Lyntech System,
Thank you for posting.
As you know, a lot of script steps / actions aren't supported on IWP. In order, to develop solution on this specific plateform, you must be aware of the numerous differences between FMP client and Web browser access through FM Web publishing engine.
On the script editor, you should use the compatibility pop-menu on the bottom left corner, and verify if all your actions are supported or not (greyed).
In the patrticular case you asked about, the show custom dialog is not. You could recreate it with your proper form layout, that contain global fields to allow user entering matching criterias.
Please note you had maybe posted in a wrong section of this forum : this one is dedicated to submit potential bugs on the software. For more information about the IWP plateform, please check the IWP Guide on help menu or go to the FM Pro Forum tab on the top of this forum.
Good luck and maybe see you soon !