Simple addition seems a bit tricky in zope <dtml-call "REQUEST.set('CategoryTotal',0)"> <dtml-in "tmp.propertyItems()"> <dtml-let key="_['sequence-key']" value="_['sequence-item']" category="s[:1]" counter="_.getitem(category+'Total')"> <--// Here i want to concatenate the category from the value with the word total so that i can lookup my declared variable in the namespace. <dtml-var expr="counter=counter+value"> <--// Here i tried to increase the declared variable with the value. </dtml-let> </dtml-in> Can someone help? Roché