Formula for capturing the latest balance

Hi,

I have a file (I'm using MS Excel 2002) with 3 sheets (please refer to attachment).

In the SUMMARY sheet, I would like cell E11 to capture the latest balance in column G of the C4 WINDOW (Machine) sheet. In this case, cell E11 should capture 11,750

And in the SUMMARY sheet again, I would like cell E12 to capture the latest balance in column G of the C5 WINDOW (Self-Adhesive) sheet. In this case, cell E12 should capture 13,500

As the latest balance in column G will change whenever there is a new entry, I was unable to use the ='sheet'!cell formula

Any help is appreciated!