inventory control

Hello,

i want to create a worksheet that informs me when tools are not in the warehouse,and who loaned has loaned it...

f.e. every thim when a user want to have a tool i want to scan the userID in colum A, and the ToolID in column B, the status must be filled in cell C (status changng from IN to OUT).

=> a user can only have 1 TOOL
=> tool can only by registrated under 1 userID

when a user is scanned but still got other Tools connected to his name => warning (Pop up)

the only way to scanin a tool back into the system is to scan the userID/toolID in column A-B and the status is changing back to IN

The problem I got is when a user/tool appears more than 1 time in the list...
Vlookup will always detects the first One...

any ideas or sources i can check

thx