Trigger an approval workflow by changing a existing cell value

Hi, I have a multi level workflow approval setup which cascades project approval requests through a series of managers. The project list consists of a sheet of agreed projects so the only way I have been able to trigger the work flow is to have a specific cell for each row which I change in smartsheet to submitt. this then triggers the workflow and away we go.  BUT BUT BUT this is a PITA, I want to be able to have a mechanism where the end user is not exposed to the smartsheet and can just use a "form"to to attach the project brief to an existing row (as an attachment) and set the trigger to submit (it would be really nice if the drop down list can be dynamically filled).

Has anybody been able to make this happen within native smartsheet.