preventing Sql Injection & killchar function to replace bad words

Hey

I would like to know if someone can help me with some advise on the following question

I have read in many 'preventing Sqlinjection articles" to use   a  killchar function to replace bad words in sql qeuries


here is an example of a code from the internet

<%

function killChars(strWords)

dim badChars
dim newChars

badChars = array("select", "drop", ";", "--", "insert",  
"delete", "xp_")
newChars = strWords

for i = 0 to uBound(badChars)
newChars = replace(newChars, badChars(i), "")
next

killChars = newChars

end function

%>

So my question would be how do I use this  with a textbox..  before it goes into a  database  query

if I'm using <%@  ValidateRequest="true ...