Why Message Boxes Repeat?

Apologize for the convoluted description - hence why I included the code.
Have tried the Application...enable true/false to no avail - agree, "something" is triggering
the msgboxes to show again, but on second time through, they do as they should - simply close.
I first thought Exit Sub was not working...but that is not the case.
Possibly, just possibly due to the fact it's the same cell (C4)for the change event - but also for the msgboxes as well...???
Thoughts, suggestions?

Cell C4 is a pull down of various chemicals from a table on a different worksheet - when the name changes - a column is cleared on the same worksheet as C4 - simple.
However, and here's the kicker, if there happens to be a particular name in that cell, C4, e.g. lead (Pb), then I "invoke" a message box which asks a question.
If the response is "yes" - then another message pop's up, whereupon I want to simply click OK, and exit, but it doesn't do that -
goes back to the first message box. If I answer the same way Yes, the OK, it exits. Same is True if I initially answer "No" to the first msgbox - a subsequent message
appears - simply making a statement, to which I click OK, and again should exit but does the same thing as above - goes again but on 2nd go through, it will exit.

I most appreciate your viewing this since there are a gazillion questions on here and I do try my very best to solve on my own. Have done good so far in this program,
but this issue as really thrown me for a big loop!!!

Best weekend wishes,
Sgt Rock (Mort in Dallas)

FYI...did as you suggest and added the Application code...

Option Explicit

Private Sub Worksheet_Change(ByVal Target As Range)

'This line of code clears the Activity column once a new chemical is selected from the select chemical drop down

Application.EnableEvents = False
    If Not Intersect(Target, Target.Worksheet.Range("C4")) Is Nothing Then Call ClearColumn
               
    If Range("C4").Value = "Lead" Then Call CheckForLead
Application.EnableEvents = True
End Sub

Now no message boxes at all appear even if Lead appears in cell C4 - this strange issue has happened at lot - I change the code a lil bit, and it stops working - have to go back to
the original workbook to get it going again...I'm stumped!!!
Best, SR

Option Explicit

Private Sub Worksheet_Change(ByVal Target As Range)

'This line of code clears the Activity column once a new chemical is selected from the select chemical drop down

Application.EnableEvents = False

On Error GoTo exitEnabled

    If Not Intersect(Target, Target.Worksheet.Range("C4")) Is Nothing Then Call ClearColumn
               
    If Range("C4").Value = "Lead" Then Call CheckForLead

exitEnabled:
Application.EnableEvents = True
End Sub

Code edited to make it safe.
Have you set a break point in the error handler and stepped through?
And searched for other calls to CheckForLead?


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