When I arrived at my current school there was NO instrument inventory system. I started keeping track on a Google spreadsheet. Eventually I pieced together enough formulas and scripts which now allows me to easily see:
Who is assigned to each instrument
What locker the instrument is stored in
The locker combination
Coming Soon: Instrument Status. I'm still working on the script, but eventually I will be able to see if an instrument has gone out for repair, or if the e-string needs replacing, etc.
The first tab (LR1) is divided up to look like my locker room. Within this tab are formulas that look up the locker combination and student name from the second tab (VN-contains all violin inventory information). You can click on individual cells should you wish to see the formulas. I am using the "VLOOKUP" formula. My husband was the one who worked out this formula using this webpage as a guide.