inputbox appear when cells outside the set range are modified

Hi guys (and girls),

Im having a slight but annoying issue on excel.

I have a form that will be used to log orders onto, the basic premise is that you select a product code from a drop down list and vlookup populates the description in the next cell. Im trying to add very basic validation using vba, so that when a product from the drop down list is selected an input box appears asking for the quantity and the puts that value in the corresponding quantity cell.

the problem is that with my current code, even if I specify only one cell as my range, when I change any of the dropdown lists the input box appears and changes the value in the first rows quantity box.

the current code is:

 Private Sub workbook_sheetchange(ByVal sh As Object, ByVal target As Range)
 On Error Resume Next
 Dim strresult As Integer
 Application.EnableEvents = False
 Set myRng = Range("c24") ' Change if necessary
 If Application.WorksheetFunction.String(myRng) <> "Select Product…" Then
 strresult = InputBox("Please enter a quantity", "Enter Quantity")
 Range("I24") = strresult
 End If
 Set myRng = Nothing
 Application.EnableEvents = True
 End Sub

any help will be greatly appreciated thanks!

When do you want the input box to appear?

By the way, there's no such thing as Application.WorksheetFunction.String.

PS Can you add code tags when posting code?

Do you have multiple dropdowns/data validation and you want this code to run whenever a selection is made in one of them?

Also, do you want the value entered in the inputbox by the user to be placed on the worksheet in the quantity cell corresponding to the dropdown the selection was made in?

Which column are the drop downs in?

With this code whenever a selection is made in a dropdown in C2:C50 the user will be prompted for a quantity.

The quantity they enter will go in column F on the same row as the dropdown the made the selection in.

Private Sub Workbook_SheetChange(ByVal sh As Object, ByVal target As Range)
Dim strresult As Integer

    If Not Intersect(target, Range("C2:C50")) Is Nothing Then

        Application.EnableEvents = False
        strresult = InputBox("Please enter a quantity", "Enter Quantity")
        target.Offset(, 3).Value = strresult
    End If
    Application.EnableEvents = True
    
End Sub

Or, that's what should happen, hopefully.