Vbsrcipt code for Anti-SQL injection _vbs

<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&G t;=48)) Then
MsgBox ("Do not use characters except English letters and numbers!") ")
Strname.value = Left (strn,i-1)
Strname.focus
Exit For
End If
Str=right (Str,len (str)-1)
Next
End Function
function Checknum ()
Checknum=true
If not document.all.txtmailsize.value= "" Then
If not IsNumeric (Document.all.txtMailSize.value) Then
MsgBox ("Do not use characters other than numbers!") ")
Document.all.txtmailsize.value= ""
Document.all.txtMailSize.focus
Checknum=false
else if document.all.txtmailsize.value>5 or document.all.txtmailsize.value<0 then
MsgBox ("Please fill in the number between 5-0!") ")
Document.all.txtmailsize.value= ""
Document.all.txtMailSize.focus
Checknum=false
End If
End If
End If
End Function

function Checkupdate ()
Checkupdate=true
If document.all.txtu_name.value= "" or document.all.txtmailsize.value= "" Then
MsgBox ("You fill in the information is not complete!") ")
Checkupdate=false
End If
End Function
function Compare ()
Compare=true
If not document.all.txtRePsw.value =document.all.txtpsw.value then
MsgBox ("Two times password input inconsistent!") ")
Document.all.txtRePsw.focus
Compare=false
End If
End Function