Bernie, I appreciate that you have weighed in here. My dilemma is this: I am
building an Excel application that my client was very clear that he wants it
to be a self-contained Excel workbook (no DLLs), he wants it protected
within reason (Excel protection is good enough); and he wants it to work in
Excel 2000 and 2003; and lastly, he wants Solver to be functional and
controllable by the user. He does not want to immitate the Solver (i.e.,
have the program manipulate Solver's variables and behavior). Adding the
Solver reference using VBA code is trivial (shown below) but the location of
Solver is unreliable, and packaging the application with a reference already
added to the VBAProject is just asking for a runtime error.
I use a button click to re-enable Solver on the Tools menu, use SendKeys to
launch it -- but then the user is on their own. A very clever user will be
able to systematically plunder hidden formulas, etc. by taking advantage of
the fact that until Worksheet_SelectionChance event occurs (which is where I
reapply worksheet protection) they can left-click a cell, and observe the
formula in the formula bar, until mouseup. So I really do need a way to tell
if Solver has been closed, maybe some routine which can count child windows
in Excel, something in API??

Sub GetSolverRef()
Dim Ref As Object, bItemFound As Boolean
For Each Ref In ThisWorkbook.VBProject.References
If UCase(Ref.Name) = "SOLVER" Then
bItemFound = True : Exit For
End If
Next
ThisWorkbook.VBProject.References.AddFromFile _
Application.LibraryPath & "\solver\solver.xla"
End Sub