防SQL注入的VBSrcipt

<script language="vbscript">

        function checkstr(strname)

            strn=trim(strname.value)

            str=trim(strname.value)

            for i=1 to len(str)

                strcheck=asc(left(str,1))

                if not ((strcheck=<122 and strcheck>=97) or (strcheck<=90 and strcheck>=65) or (strcheck<=57 and strcheck>=48)) then

                    msgbox("请勿使用除英文字母及数字以外的字符！")