x,y,z=100% - if x = 77, what value y and z...

[ggsmit]

hi
math has never been my forte, never mind excel :-/
the problem:
i have to make a mixture of three substances that have to make 100% [per mass].
substance x = 77% of the mixture
substance y = 18% of the mixture
substance z = 5% of the mixture
total=100%
i want to have/make a macro or run a vba or set up a sheet where i can enter values for x y or z and get the rest of the calculation done for me.
any help will be more than welcome!
in Christ
gabriel smit

[Bob Phillips]

This code goes in the sheet code modulke and automatically updates whe A2, A3 or A4 is changed. It assumes A2 is x, A3 is y, and A4 is z

Private Sub Worksheet_Change(ByVal Target As Range)

    On Error GoTo ws_exit
    
    Application.EnableEvents = False
    
    Select Case True
    
        Case Not Intersect(Target, Me.Range("A2")) Is Nothing
        
            Me.Range("A3").Value = Target.Value / 77 * 18
            Me.Range("A4").Value = Target.Value / 77 * 5
    
        Case Not Intersect(Target, Me.Range("A3")) Is Nothing
        
            Me.Range("A2").Value = Target.Value / 18 * 77
            Me.Range("A4").Value = Target.Value / 18 * 5
    
        Case Not Intersect(Target, Me.Range("A4")) Is Nothing
        
            Me.Range("A2").Value = Target.Value / 5 * 77
            Me.Range("A3").Value = Target.Value / 5 * 18
    End Select


ws_exit:
    Application.EnableEvents = True
End Sub

[ggsmit]

thank you bob, it works 100%!
yours in Christ Jesus,
gabriel

ps, how do i mark this as solved?