Peter,
There are a number of steps you can take to make this happen. Note that it will require code changes to really 'lock down' access to older versions. If someone would know the ID of an older version he/she could still download it as they would still have access rights. But if security by obscurity is sufficient you can do the following:
1. In the ViewDetails.ascx file you will find 2 <dmx:panel enclosures: one around the Version History, the other around the Log. Both of these have a 'viewpermission' setting that can be altered. In your case you'd want to alter the first enclosure to have viewpermission="admin". This will remove it from view for non-admins.
2. In Search.ascx you'll find the following line:
 <asp:checkbox runat="server" id="chkAllVersions" text="All Versions" resourcekey="chkAllVersions" />
You can put an enclosure around this in similar fashion to point 1 above. In other words:
 <dmx:panel id="pnlAllVersions" runat="server" viewpermission="edit">
  <asp:checkbox runat="server" id="chkAllVersions" text="All Versions" resourcekey="chkAllVersions" />
 </dmx:panel>
This will remove the checkbox from view. By default DMX should not search older versions, so this should be sufficient for your cause.

Peter

Peter,

I have just started back at work and tried your suggestions on my test server.

Firstly it seems that it does search older versions in the basic search (by default) and the checkbox is selected by default in the search area.

Secondly I do not have panels in the viewdetails.ascx file that have dmx:panel enclosures the following is an extract of the code I  have for this page.<asp:panel id=pnlVersionHistory runat="server">

<p><asp:hyperlink id=hlHyperlink runat="server" /></p>

<asp:panel id="pnlVersionHistory" runat="server" >
 <h2>
  <img src="<%= DMXPath %>images/DMX32.gif" align=absBottom>&nbsp;
  <asp:label runat="server" id="lblVersionHistory" resourcekey="lblVersionHistory" />
 </h2>
 <asp:datagrid id="dgHistory" width="100%" runat="server" cellspacing="0" cellpadding="2" border="0" gridlines="none" autogeneratecolumns="False" showheader="True" cssclass="DetailsGrid_Container" itemstyle-cssclass="DetailsGrid_Item" alternatingitemstyle-cssclass="DetailsGrid_AlternatingItem" headerstyle-cssclass="DetailsGrid_Header" PagerStyle-cssclass="DetailsGrid_Pager">
  <itemstyle verticalalign="Top" />
  <columns>
   <asp:TemplateColumn HeaderText="Uploaded" itemstyle-width="120">
    <itemtemplate>
     <p class='<%# IIF(DataBinder.Eval(Container, "DataItem.EntryId") = Query.EntryId, "DMX_SelectedRow", IIF(GetAString(DataBinder.Eval(Container, "DataItem.Entry"))="", "DMX_DeletedRow", "DMX_NormalRow")) %>'>
      <a href='<%# DMXUrl(DataBinder.Eval(Container, "DataItem.EntryId")) %>'>
       <%# CType(DataBinder.Eval(Container, "DataItem.DateSubmitted"), Date).ToShortDateString %>
       <%# CType(DataBinder.Eval(Container, "DataItem.DateSubmitted"), Date).ToShortTimeString %>
      </a>
     </p>
    </ItemTemplate>
   </asp:TemplateColumn>
   <asp:TemplateColumn HeaderText="By" itemstyle-width="90">
    <itemtemplate>
     <p class='<%# IIF(DataBinder.Eval(Container, "DataItem.EntryId") = Query.EntryId, "DMX_SelectedRow", IIF(DataBinder.Eval(Container, "DataItem.Deleted"), "DMX_DeletedRow", "DMX_NormalRow")) %>'>
      <%# DataBinder.Eval(Container, "DataItem.Fullname") %>
     </p>
    </ItemTemplate>
   </asp:TemplateColumn>
   <asp:TemplateColumn HeaderText="Version" itemstyle-width="110">
    <itemtemplate>
     <p class='<%# IIF(DataBinder.Eval(Container, "DataItem.EntryId") = Query.EntryId, "DMX_SelectedRow", IIF(DataBinder.Eval(Container, "DataItem.Deleted"), "DMX_DeletedRow", "DMX_NormalRow")) %>'>
      <%# DataBinder.Eval(Container, "DataItem.Version") %>
<%# IIF(DataBinder.Eval(Container, "DataItem.EntryId") = Query.EntryId, " (This Version)", IIF(DataBinder.Eval(Container, "DataItem.Deleted"), " (Deleted)", "")) %>
     </p>
    </ItemTemplate>
   </asp:TemplateColumn>
   <asp:TemplateColumn HeaderText="Remarks">
    <itemtemplate>
     <p class='<%# IIF(DataBinder.Eval(Container, "DataItem.EntryId") = Query.EntryId, "DMX_SelectedRow", IIF(DataBinder.Eval(Container, "DataItem.Deleted"), "DMX_DeletedRow", "DMX_NormalRow")) %>'>
      <%# GetAString(DataBinder.Eval(Container, "DataItem.Remarks"), 60) %>
     </p>
    </ItemTemplate>
   </asp:TemplateColumn>
  </columns>
  <pagerstyle mode="NumericPages" />
 </asp:datagrid>
</asp:panel> 

<asp:label id=lblVersionHistory resourcekey="lblVersionHistory" runat="server">I can hide previous version by editing original document first and deselecting staff view permission and updating and then uploading new document.  The older version is then only viewable by admin staff.

<asp:label resourcekey="lblVersionHistory" runat="server">Any assistance would be appreciated

<asp:label resourcekey="lblVersionHistory" runat="server">Thanks

<asp:label resourcekey="lblVersionHistory" runat="server">Peter