MySQL Table Update when a user registers for the forum?

[shellx]

Hello,
I added some custom code of mine to one of the signup php scripts that a user would fill out when they wanted to signup to be a member on our vB board. The trouble was was that it would update my "login" mySQL table in another datbase, however it would then return an error to the user, and not update them in the vBulletin membership tables (it partially adds them). If anyone has done this succesfully and would be able to tell me where i should place my code (which file, which area, etc), it'd be helpful.
I get the following error when I try to update:

Invalid SQL: INSERT INTO userfield (userid,field1,field2,field3,field4) VALUES (46,'','','','')

Thanks

[shellx]

Someone has to have done this!!!!! I think I am editing the right file (global.php won't work from what i've analyzed), but it simply is the fact of trying to get the thing to update my database and not mess up when it tries to update vB's database. It may be in the function calls; I first tried using functions such as mysql_fetch_array, but then I used vB's own class in db_mysql.php to see if that'd fix things. I feel as if I am very close, just need that silver bullet to get this going.