Dynamic Table and cross section Table manipulation

Dear Experts,

I have an expanding table, tableA as shown

tableA
stockID portfolio0 return date
Apple   0.3        0.1    199901
IBM     0.2        -0.3   199901

In the next period, expanding tableA increases a column as shown

tableA
stockID portfolio0 portfolio1 return date
Apple   0.5        0.1        0.6    199902
IBM     0          -0.2       0.4    199902

TableA will keep expanding a column at a time until it has 10 columns.

tableA
  stockID portfolio0 portfolio1 ... portfolio9 return date
  Apple   0.5        0.1        ... 0.6        0.6    199910
  ....
  Snap    0.2          -0.2     ... -0.4       -0.2   199910

Now we need to calculate total returns for each portfolio in a new tableB.

It is calculated by

sum(tableA.portfolio0 .* tableA.return)

From the first tableA, tableB becomes

tableB
portfolio0 date
-0.3       199901

According to second round of tableA, the total returns are

    portfolio0 = sum(tableA.portfolio0 .* tableA.return)
    portfolio1 = sum(tableA.portfolio1 .* tableA.return)

table B becomes

tableB
portfolio0 portfolio1 date
-0.3       0          199901
 0.3       -0.2       199902

This whole process repeats until tableA reaches 10 columns with portfolio0- portfolio9 and it will remain as 10 columns while the values for the portfolioX, return, date changes. TableB will eventually look like

tableB
  portfolio0 portfolio1 portfolio2 ... portfolio9 date
  -0.3       0          0              0          199901
   0.3       -0.2       0              0          199902
   XX        XX         XX             0          199903
   ....
   XX        XX         XX             XX         199910
   ....
   XX        XX         XX             XX         201703

Any ideas?

Thank you so much LL