Create a month table with existing projects

Hi.

The reason im trying to create this table is because:

- My goal is to make a diagram pr. month that shows risk change in the balance as accumulated values across all projects.

My problem occurs with the financial transactions which in not all months have a transaction (for example one project can only have a change 4 months a year instead of all 12, then it wouldnt be a problem. The months in between then shows a zero value instead of the last one. If you have a quick solution i would love it.

Im trying to solve it by automatically create a monthly table with for example 201801-202801 and then use columns b, c, d to list every projects accumulated value pr. month and then make the table.

Help!

            Project A - Project B

201801 500'           200'

201802 1000       

201803                   250'

201804 1100          300'