QGIS Composer - Read entered textbox value in another textbox

I’m Limited to QGIS 2.18 composer for several reasons.

I have two textboxes.

BOX1 – User INPUT value, where user enters an integer value.
BOX2 needs to read this value to be able to calculate results.

Can I use the item_uuid to read value in BOX1 to calculate a result in BOX2?
If so, what expression would this be?