Unexpected String Results

Question

I have the following code to check values entered into two input boxes, if both values are zero then the MsgBox should display "Stop!" (I will change this later to exiting the sub but I am using a MsgBox for testing)

From testing I've seen these results:

• A zero in both strings produces the expected message box.

• A non zero in the first string followed by any non zero value in the second string does nothing (as expected).

• A zero in the first string followed by a second string value equal to or greater than 10 produces the message box (unexpected).

I've also noticed that if the second string is 6-9 it is displayed as x.00000000000001%. I think this is a floating point issue and could be related? This behaviour occurs without the IF... InStr function too.

Option Explicit
Sub Models()
    Dim MinPer As String, MaxPer As String, Frmula As String
    Dim Data As Worksheet, Results As Worksheet
    Set Data = Sheets("Data")
    Set Results = Sheets("Results")

    Application.ScreenUpdating = False

    MinPer = 1 - InputBox("Enter Minimum Threshold Percentage, do not include the % symbol", _
    "Minimum?") / 100
    MaxPer = 1 + InputBox("Enter Maximum Threshold Percentage, do not include the % symbol", _
    "Maximum?") / 100


    If (InStr(MinPer, "0") = 0) And (InStr(MaxPer, "0") = 0) Then
    MsgBox "STOP!"
    End If

    ' Remainder of code...

This is the most interesting problem I've come across so far in VBA and welcome any discussion about it.

Edit: I use this code to display on screen the paramaters for the end-user to see. Hence how I noticed the .00000000001% issue:

    .Range("D2").Value = "Min is " & 100 - MinPer * 100 & "%"
    .Range("D3").Value = "Max is " & MaxPer * 100 - 100 & "%"

Answer 1

Two things

1) Declare MinPer, MaxPer as Long or a Double and not a String as you are storing outputs from a calculation

2) Don't directly use the InputBox in the calculations. Store them in a variable and then if the input is valid then use them in the calculation

Dim MinPer As Double, MaxPer As Double, Frmula As String
Dim Data As Worksheet, Results As Worksheet
Dim n1 As Long, n2 As Long

Set Data = Sheets("Data")
Set Results = Sheets("Results")

Application.ScreenUpdating = False

On Error Resume Next
n1 = Application.InputBox(Prompt:="Enter Minimum Threshold Percentage, do not include the % symbol", _
Title:="Minimum?", Type:=1)
On Error GoTo 0

If n1 = False Then
    MsgBox "User cancelled"
    Exit Sub
End If

On Error Resume Next
n2 = Application.InputBox(Prompt:="Enter Maximum Threshold Percentage, do not include the % symbol", _
Title:="Maximum?", Type:=1)
On Error GoTo 0

If n2 = False Then
    MsgBox "User cancelled"
    Exit Sub
End If

If n1 = 0 And n2 = 0 Then
    MsgBox "STOP!"
End If

MinPer = 1 - (Val(n1) / 100)
MaxPer = 1 + (Val(n2) / 100)