For anyone else that may find this helpful...

{00000409-78E1-11D2-B60F-006097C998E7} = Office 2000 Premium
{00010409-78E1-11D2-B60F-006097C998E7} = Office 2000 Professional
{00020409-78E1-11D2-B60F-006097C998E7} = Office 2000 Standard
{90110409-6000-11D3-8CFE-0050048383C9} = Office XP Professional
Office8.0 = Office 97 Professional

code:
 
$office = readvalue("HKLM\Software\Microsoft\Windows\CurrentVersion\Uninstall\{00010409-78E1-11D2-B60F-006097C998E7}","DisplayName")
If $office = ""
   $office = readvalue("HKLM\Software\Microsoft\Windows\CurrentVersion\Uninstall\{00000409-78E1-11D2-B60F-006097C998E7}","DisplayName")
Endif
If $office = ""
   $office = readvalue("HKLM\Software\Microsoft\Windows\CurrentVersion\Uninstall\{00020409-78E1-11D2-B60F-006097C998E7}","DisplayName")
Endif
If $office = ""
   $office = readvalue("HKLM\Software\Microsoft\Windows\CurrentVersion\Uninstall\{90110409-6000-11D3-8CFE-0050048383C9}","DisplayName")
Endif
If $office = ""
   $office = readvalue("HKLM\Software\Microsoft\Windows\CurrentVersion\Uninstall\Office8.0","DisplayName")
Endif