I can't read 2007+ databases.
If you are checking a specific character for a specific value you can use the MID function
So let's say on your form:
MODELNUMBER is your F054VHN
COMPRESSORMODEL is ZP103KCE-TF5-455
if you are trying to see if the 11th character of COMPRESSORMODEL is equal to the first character of the MODELNUMBER
you would have to set up something in the BEFORE UPDATE event something like
Code:
if left([MODELNUMBER],1) <> mid([COMPRESSORMODEL],11,1) THEN
Msgbox "Model Number Mismatch"
endif