I need to calculate a checksum byte for NEC LCD monitor strings. It's an XOR of most of the bytes in a single hex string. Each string I need (just power and inputs) is fairly long, and though I could do this manually using a calculator, that's tedious and error prone enough to make me look for an automatic solution.

I found this thread about creating an Excel Visual Basic module:
[Link: mrexcel.com]
but I can't get it to compile, even though I've installed the analysis add-in and gone into tools->references and ticked atpvbaen.xls.

I've also heard of a simple checksum calculator available from RTI, but I've not come across it yet.

Can anyone help out with this?