Here is what you need to use in a Global Page Script. Replace the 92 in $ITEMSTATE92 with the actual ID of your item (can be found next to the name of your item on the item page). Also, replace the variable enclosed in quotes, so $PAGETEXT + "%%ITEM92VAR%% can be replaced with whatever variable you wanted.
IF $ITEMSTATE92 = 1 THEN
$PAGETEXT := $PAGETEXT + "%%ITEM92VAR%%"
If you want you can display a whole different text for the page if your item is being held line would be:
$PAGETEXT := "This is the new description"
Also, you can include the old pagetext (the original) and add more writing:
$PAGETEXT := $PAGETEXT + "This some extra description and you can display variables like %%VARIABLEHERE%% this."