Referring to the post in General Question

Does anyone have any suggestion on following coding?

Following code is to generate a prime number in cell B1 by typing a number
in cell A1, if I type 1 in cell A1, then it will return the first prime
number 2 in cell B1,
if I type 2 in cell A1, then it will return the first prime number 3 in cell
B1,
I would like to set a formula to change the number in cell A1, such as
in cell A1, =A2+A3, when I change any value in cells A2 or A3, the return
prime number in cell B1 cannot be automatically updated. Does anyone have any
suggestions? I still want to return the prime number in cell B1 based on the
value in cell A1. A1=A2+A3 is just a simple example for formula.
Does anyone have any suggestions?
Thank everyone for any suggestions
Eric

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Coding
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Select the sheet you want to use and right-click the sheet tab. Select view
code and paste this in exacly as below:-

Private Sub Worksheet_Change(ByVal Target As Range)
If Target.Cells.Count 1 Or IsEmpty(Target) Then Exit Sub
If Target.Address = "$A$1" Then
If IsNumeric(Target) Then
On Error Resume Next
For x = 1 To 10000
Dim i As Long
If x < 2 Or (x < 2 And x Mod 2 = 0) Or x < Int(x) Then GoTo 100
For i = 3 To Sqr(x) Step 2
If x Mod i = 0 Then GoTo 100
Next
foundprime = foundprime + 1
If foundprime = Target.Value Then
Target.Offset(0, 1).Value = x
Exit Sub
100
End If
Next
On Error GoTo 0
End If
End If
End Sub

Close the VB editor and then enter 50 in a1 and the 50th prime will be
displayed in B1.