Pulling line numbers from last months invoice to this months invoice

[Anon User13]

I have uploaded a sample file to make this easier so please take a look at it.

What I want to do is pull in the line numbers (column H) from the first tab (Aug) to the second tab (Sept)(Column H). I need to compare Column A, B and D to make sure I am choosing the correct line number. Now the Sept invoice has some new lines added to it so I realize those won't come back with any results since no line number exists for them yet. However, it would be great if I didn't have to manually type in all of the line numbers every month after visually comparing to the month before. Let me know if I need to clarify.

 

[azumi]

Put this on H2 on Sheet "Sept"
=IFERROR(INDEX(Aug!$H$2:$H$15,MATCH(1,(Aug!$A$2:$A$15=$A2)*(Aug!$B$2:$B$15=$B2)*(Aug!$D$2:$D$15=$D2),0)),"")

and press F2 button, and you'll see the formula, after that press/hit CTRL+SHIFT+ENTER button/key all together, ENTER alone not working, if success you'll see the bracket "{}" that exclosed the formula, final setp copied down the formula as necessary.......

 

[Anon User13]

Thank you very much! This is a huge help!