Updating visiblity for a Sales Order factbox from selecting lines on the Sales Order Subform

Hi,

I've got a factbox that is located as a part on the Sales Order page. What I simply need to do is if the 'Type' of Item in a sales line is of type 'Service', then this factbox's visiblity will be set to false and disappear. Example: If I have two lines in the sales order subform, one of Item type 'Inventory' and one of Item type 'Service' - if i select the line of type 'Inventory' then the factbox on the sales order will be visible. If i select the line of type 'Service' then the factbox will disappear. I cannot seem to find a way to pass a variable to the Sales Order page 'OnAfterGetRecord' for the sales line in order to dynamically set the visibility. I can set filters etc fine by using the SubPageLink, but I cannot control the visiblity. I've been racking my brain with this all day, so any ideas would be much appreciated!

Thankyou