How do i write an excel formula that can work either ways?

[chimezie oleka]

I want to write an excel formula that can compute commission charged using simple interest rate. The fields will be:

1. Amount
2. Percentage
3. Commission charged

How do i write a formula that can provide answers to any field once the other two fields have been completed?

 

[chimezie oleka]

Your formulae worked. It is even better. I had issues with the space between the hyphen. You are good.

 

[jolivanes]

Thanks chimezie oleka.
But you'll have to put the formulae in the cells every time after use, right.
Put this in the sheet module and try it.
Or you could use this.

Private Sub Worksheet_Change(ByVal Target As Range)
    Dim tarCells As Range
    Set tarCells = Range("D8:D10")    '<----- Change as required
    
    If Not Application.Intersect(tarCells, Range(Target.Address)) _
           Is Nothing Then
    Select Case WorksheetFunction.CountA(tarCells)
        Case Is = 0
            Exit Sub
        Case Is = 1
            Exit Sub
        Case Is = 2
            If Cells(10, 4) = "" Then
                Cells(10, 4).Value = Cells(8, 4).Value / 100 * Cells(9, 4).Value
            ElseIf Cells(9, 4) = "" Then
                Cells(9, 4).Value = Cells(10, 4).Value / (Cells(8, 4).Value / 100)
            ElseIf Cells(8, 4) = "" Then
                Cells(8, 4).Value = 100 * (Cells(10, 4).Value / Cells(9, 4).Value)
            End If
    End Select
    End If
End Sub

The range where you use your values is D8 to D10.
Put values in any two cells in this range and you'll get the result in the third cell
You will need to change all the cell references depending on where you'll need it

 

[jolivanes]

I forgot to mention to clear the three cells before your next calculation
You can do that if you select another sheet and then this one again if you put this in the sheet module also

Private Sub Worksheet_Activate()
    Range("D8:D10").ClearContents
End Sub