Case Sensitive In Replace Function In ASP

I use a replace char function to remove any bad words from user's input to prevent SQL injection. Here is what I use:

Function killChars(strWords)
Dim badChars, newChars
badChars = Array("bad words here")
newChars = strwords
For i=0 to uBound(badChars)
newChars = replace(newChars, badChars(i), "")
next
killChars=newChars
End function

Now the problem is if a user enter "DeLETe" in the input box, and this word is not get removed before entering the DB. because I entered "delete" in the badchars array.

so how can I enable a case sensitive in my function? So the bad words would get deleted regardless its in upper or lower case?