property HTTP.InField(FieldName as String) as String
Specifies the value of the field before getting the URL.

TypeDescription
FieldName as String A String expression that indicates the name of the field being added to the GET header, before sending the request.
String A String expression that indicates the value of the field.
The InField property retrieves or specifies the "request" fields. If the FieldName parameter is empty,  the InField property retrieves all the fields in the GET header. Use the InField property to add addition fields to the GET request. The RFC 2616, explains better all the fields that may be used. The OutField property lists the repose fields. Use the GET method to retrieve a document or a web page.

Shortly here they are: