I assume by ASP code you mean ASP variables? If so this should work below...
Code:
<html>
<head>
...
</head>
<body>
<%
dim iNumber
dim szString
iNumber = 1000
szString = "Monkeys"
' Open FSO and your text file..
FSO.WriteLine("I have" & iNumber & " " & szString & " living in my garden")
%>
</body>
</html>
All you have to remember is that anything between the " "s is string data, and anything outside of them is ASP. The & is used to stick the two together.
In the example above, the text in your file would read -
I have 1000 Monkeys living in my garden.
HTH!