Performance-String Searching

Hi,

Does anyone have any suggestions on an approach to speed this up
please?

I need to check a given column in a given table to see whether there
are any characters within any of the records that fall outside of a
range of valid ASCII characters.

My problem is that of speed. The approach I have taken is to write a
function that iterates the string character by character and checks the
ASCII value at the current position. If it is deemed invalid I drop out
of the function and return True. The calling procedure then knows to
stop searching as the table column has already failed.

Running down a table of million rows, can take up to an hour depending
on the datatype and level of data population.

If I write the same thing in Access 2003 VBA and run it via ODBC it
takes a matter of minutes.

I would like to find a set-based way of doing this maybe PATINDEX or
something else creative but am stumped.

Does anyone have any brilliant ideas?

Thank you!