Having once designed a help desk database (never got the funding to implement it...), we learned that there are many ways to do this, but the best way is to know EXACTLY what the error messages will resemble.
For example, VBA messages are a number and some text. The text involves lots of file names and other parameters, but the number is always the same. So you might have fields that say, "VBA", "2079" - meaning this is VBA number 2079. Another entry might say "WINXP", "EXC 5" - meaning a WINXP error with exception code 5.
The essence is to identify the part that is invariant and then know what to ask your caller.
On the other side of the coin, do you charge back for each call? (I.e. is this a pay-per-service, warranty, contract thing - or a business's internal thing?) Find out how you need to record information that will account for your time. Trust me, someone is eventually going to want to know that.
Not to discourage you, but there are some really good packages out there that already handle help desk stuff. There is even an organization of help desk support workers and they have neat conventions. I cannot tell you the cost of doing so, but if it is going to be a large enough organization, you might want to look like a genius and suggest not re-inventing the wheel.
