Stock Portfolio - Aggregating over multi sheets

Hey guys

I'm creating a spreadsheet to keep track of my stock holdings.

I've got several portfolios. Each of these portfolios is in its own "sheet"

I'm wanting to create a summary sheet which will total up my holdings in each stock.

eg

Portfolio 1 - Sheet 1
ABC 2000 shares
XXX 1500 shares
XZY 1000 shares

Portfolio 2 - Sheet 2
ABC 1000 shares
XZY 8000 shares

Portfolio 3 - Sheet 3
TTT 500 shares

So the summary sheet would collate the holdings over multiple sheets and produce something that looks like this

Summary - Sheet 4
ABC 3000 shares
XXX 1500 shares
TTT 500 shares
XYZ 9000 shares

Obviously if I add a new stock to one of the individual portfolios this needs to be automatically updated in the summary.

Can anyone give me any guidance on the excel formula to do this?

Cheers

Thanks. Issue solved