Evaluate a passed string variable

[Mihail]

Hi all !
I am looking for a way to evaluate string expressions.
I know about SCRIPT control but this control can't do my job.
Basically I wish to calculate functions. Something like this:

Say I have a mathematically function: y = E(x) where E is an expression I don't know at design time. So I need to calculate y by evaluate E at run time. Something like this:

Sub Test
Dim Y as Double, x As Double, E as String
 
    x = 2
    E = "x + 5"
    Y = Fx(x,E)
    Debug.Print Y 'Should return 7
 
    E = "3*x+4"
    Y = Fx(x,E)
    Debug.Print Y 'Should return 10
End Sub
 
Private Function Fx(x As Double, Ex As String)
    Y = Value of Ex ??????
End Function

Of course the functions I need to evaluate are more complicated than this so I am looking for a general procedure.

Can you help me ?
Thank you !

[Guido Geurs]

add the component "ScriptControl" to the form.
This is the code for the calculation:

Private Sub Command1_Click()
   Call Test
End Sub
 
Sub Test()
Dim Y As Double, x As Double, E As String
 
    x = 2
    E = "x + 5"
    Y = Fx(x, E)
    Debug.Print Y 'Should return 7
 
    E = "3*x+4"
    Y = Fx(x, E)
    Debug.Print Y 'Should return 10
End Sub
 
Private Function Fx(xval As Double, Ex As String) As Double
Dim EVALstring  As String
   EVALstring = Replace(Ex, "x", Str(xval))
   Fx = ScriptControl1.Eval(EVALstring)
End Function

[Mihail]

Thank you Guido !
I did not know the function "Replace".
I use a lot of extra code to replace the value of variable in Ex.

Thank you again.