Not sure exactly what you mean here.. but you could try using Aggr() and aggregating around the Month dimension value only for the line chart. So if your expression for the line chart is sum(Sales) for example you could try sum(Aggr(sum(Sales),Month)). Not sure if this will work.. or look nice for that matter.
I mean, when we create a combo stacked bar chart, how can we let the line not following the second dimension?
I can do this easily like the following suggestion, but the problem is i am doing it on material code. which will be too many to hard code one by one.
there's a manual solution here - http://community.qlik.com/thread/10783