Re: Is is possible to apply lookup in the same module to pick value of the previous line item?
We can use the lookup formula in the same module. The below module contains "Headcount" as dimension. I used the Lookup function to identify the Manager's Geo (screenshot below). Format of the Manager line item should be "Headcount".
@SathyaM answer is a good one. You can certainly use Lookup in the same module (not sure that's the most efficient way though).
I had one follow up question for you though - Did you want the previous "line item", as you wrote? That might be a little harder. Maybe if you shared a mocked-up screenshot we can add more clarity to what you're trying to accomplish.