You can probably use worksheet script to trigger a piece of LT script when data in a column gets changed. Please access the dialog from menu Worksheet->Worksheet Script...
And what if I can't use the worksheet script? Worksheet script is fine for making templates, but what if in case I'm not looking for a template solution, but building a, say X-function, that reads something from the source worksheet and create a graph as result. I don't want to put redundant datasets in wks just for holding the green lock.