Calculations in Portals

[Gideon Whitecloud]

Hi,

Am doing my first project  as a beginner with Filemaker Pro 12 and am stuck at a point. Please help me out on what to do.

am using these fields in a portal:

Opening Stock, Closing Stock, Quantity Received, Quantity Sold and Stock Balance

So

for the first step: Opening Stock = Stock Balance

then for the other steps or next inputs: Stock Balance is to = Quantity Received - Quantity Sold.

Now, at the end inputs (say for 10 rows), the last value of the Stock Balance is automatically the Closing Stock.

Please how can I do this? Is it possible in portal and if not, how can I achieve this

[eos]

Your description has no context.

It would be helpful if you tell us what your solution is supposed to manage in real life terms, as well as list your tables and explain their relationships.