Safeguarding Injection

I have written several site functions to hopefully prevent against cross-site hacking, sql injection, and url encoding. I also have a symetric key encryption that is pretty basic (which isn't posted here and is total overkill). I was wondering if these functions are protecting well enough, or am I missing some tests?

Function InjFix(val)
InjFix=SEncode(Trim(Replace(val,"'","''")))
end Function

Function SEncode(val)
SEncode=Server.HtmlEncode(val)
end Function

Function URLEncode(val)
URLEncode=Server.URLEncode(val)
end Function