[Zope] Uppercasing a string in a ZSQL method?

I've tried the following to change a string to upper case in a ZSQL method: <dtml-sqlvar sNewAcctNo type=string upper> (doesn't work; sqlvar doesn't define 'upper') <dtml-let sNewAcctNo="_.upper(sNewAcctNo)"> (doesn't work; exceptions.AttributeError) <dtml-let sNewAcctNo="string.upper(sNewAcctNo)"> (doesn't work; exceptions.NameError) <dtml-let sNewAcctNo="upper(sNewAcctNo)"> (doesn't work; exceptions.NameError) What am I missing? Thanks in advance, -scott