Classic ASP Functions and Sub Procedures

Last updated: August 25, 2026.

VBScript procedures let a Classic ASP page group reusable logic. A Sub performs an action, while a Function returns a value by assigning it to the function’s name.

Write and call a Sub

<%
Sub WriteGreeting(ByVal personName)
    Response.Write Server.HTMLEncode("Hello, " & personName)
End Sub

Call WriteGreeting("Sam")
%>

Write and call a Function

<%
Function LineTotal(ByVal quantity, ByVal unitPrice)
    LineTotal = CDbl(quantity) * CCur(unitPrice)
End Function

Dim total
total = LineTotal(3, 19.95)
Response.Write FormatCurrency(total)
%>

Parameter behavior

• Use ByVal when the procedure should not replace the caller’s variable.
• Use ByRef only when modifying the caller’s variable is intentional.
• Parentheses are used when a function result is part of an expression.
• Keep database access and HTML output separate when procedures grow complex.
• Encode untrusted output with Server.HTMLEncode.

Microsoft’s Classic ASP documentation describes procedural processing in ASP.