You can use code like this to add VBA code to a workbook:

Sub AddMeanModuleAndWickedProcedure()

Dim newVBComp As VBComponent
Set newVBComp = ActiveWorkbook.VBProject.VBComponents.Add(vbext_ct_StdModule)
newVBComp.Name = "ReallyDangerousCode"

With newVBComp.CodeModule
  .InsertLines .CountOfLines + 1, _
               "Sub myKillerSub()" & Chr(13) & _
               "   Msgbox ""Hello There, I'm about to destroy your computer.... HA HA HA HA!!!!"" "
& Chr(13) & _
               "End Sub"
End With
End Sub

It requires a reference to the MS VBA Extensibility X.X  (Sorry, I mis-spoke when I said VBIDE
Extensibility) to work, and this was the basis of that Word virus that made headlines 5 years or so
ago.  You can see where adding code to workbooks can be problematic, especially if the code is
written in a way that it writes itself into all open workbooks, which then write code to....

Bloodhound may also look for file deletion or kill commands..  I'm not certain of what it looks for,
but I lost lots of code like that above  when I was writing a utility that would update the code in
files created from a template....

HTH,
Bernie
MS Excel MVP