Thanks DreXor,
I found that this works:
dim fsoObj, sFileName, objtextFile, fieldName, fieldValue
sFileName = server.MapPath("test.csv")
set fsoObj = Server.CreateObject("Scripting.FileSystemObject")
set objtextFile = fsoObj.OpenTextFile(sFileName, 8)
For ix = 1 to Request.Form.Count
fieldName = Request.Form.Key(ix)
fieldValue = fieldValue&Request.Form.Item(ix)&","
Next
objTextFile.WriteLine(fieldValue)
objTextFile.Close
set objTextFile = nothing
set fsoObj = nothing