Hi Niek:

Thanks for gettingn back to me. Is there something I am missing to see in
your example? I wanted to create a UDF to take inputs(constraints) then
trigger solver and return the output to the cell. I am fairly (no prior VB
experience) new to these kind of advanced things and I would appreciate if
you can help me understand in a few words.

Regards.

"Niek Otten" wrote:

Maybe this:

' ================================================== =================
Function Backward(ValueToBeFound As Double, MoreArguments As Double, _
Optional ReasonableGuess, Optional MaxNumberIters, _
Optional MaxDiffPerc) As Double
'
' Niek Otten, March 22 2006
'
' This EXAMPLE function goalseeks another function,
' called Forward. It works for almost any continuous function,
' although if that function has several maximum and/or minimum
' values, the value of the ReasonableGuess argument becomes
' important.
' It calculates the value for ReasonableGuess and for
' 1.2 * ReasonableGuess.
' It assumes that the function's graph is a straight line and
' extrapolates that line from these two values to find the value
' for the argument required to achieve ValueToBeFound.
' Of course that doesn't come out right, so it does it again for
' this new result and one of the other two results, depending on
' the required direction (greater or smaller).
' This process is repeated until the maximum number of calculations
' has been reached, in which case an errorvalue is returned,
' or until the value found is close enough, in which case
' the value of the most recently used argument is returned

Dim LowVar As Double, HighVar As Double, NowVar As Double
Dim LowResult As Double, HighResult As Double, NowResult As Double
Dim MaxDiff As Double
Dim NotReadyYet As Boolean
Dim IterCount As Long

If IsMissing(ReasonableGuess) Then ReasonableGuess = 1.5 ' use default Values
If IsMissing(MaxNumberIters) Then MaxNumberIters = 20 ' that make sense in the
If IsMissing(MaxDiffPerc) Then MaxDiffPerc = 0.001 ' context of the function

MaxDiff = ValueToBeFound * MaxDiffPerc
NotReadyYet = True
IterCount = 1
LowVar = ReasonableGuess
LowResult = Forward(LowVar, MoreArguments)
HighVar = LowVar * 1.2
HighResult = Forward(HighVar, MoreArguments)

While NotReadyYet
IterCount = IterCount + 1
If IterCount MaxNumberIters Then
Backward = CVErr(xlErrValue) 'or some other errorvalue
Exit Function
End If

NowVar = ((ValueToBeFound - LowResult) * (HighVar - LowVar) + LowVar _
* (HighResult - LowResult)) / (HighResult - LowResult)
NowResult = Forward(NowVar, MoreArguments)
If NowResult ValueToBeFound Then
HighVar = NowVar
HighResult = NowResult
Else
LowVar = NowVar
LowResult = NowResult
End If
If Abs(NowResult - ValueToBeFound) < MaxDiff Then NotReadyYet = False
Wend

Backward = NowVar

End Function
' ================================================== =================

Function Forward(a As Double, b As Double) As Double
' This is just an example function;
' almost any continous function will work
Forward = 3 * a ^ (1.5) + b
End Function
' ================================================== =================




--
Kind regards,

Niek Otten
Microsoft MVP - Excel

"Murthy" wrote in message ...
| Hi all:
|
| Can someone give me an idea of how to define excel solver as an user defined
| function? Say A3 = CallSolver(Inputs, Retrun Output)... something in those
| lines.
|
| Regards.
|