I am trying to create a dynamic hyperlink within a mail merge document.

The root of my URL is held within the Hyperlink base, the page name is
within a merge field, and am just adding the htm extension onto the back of
it.

However, whenever i encompass this within the HYPERLINK key field all i get
is the hyperlink base. My code is as follows:

{Hyperlink {Docproperty HyperlinkBase} {MERGEFIELD Document_id} ".htm" }

Any suggestions as to why it's not working???

Many thanks in advance to you all