You can move triggers around with SetPos:
triggername SetPos [x,y,z]
or, for you:
triggername SetPos (GetPos hostage)
The tricky bit is the triggername. In my editor, the 'Name' and 'Text' fields on the Trigger's dialogue box are crossed over - what you type in the 'Text' field actually becomes the name of the trigger!
Might need to watch how often you update it's position if you're using countdown or timeout. Hope it helps . . .