Excel Macro suddenly starts giving incorrect ActiveCell Data

[simora]

I've been asked to provide more of the full Macro rather than just the offending portion.
Here's more or less the full bit to get an idea of what it does.


After trying all of the suggestions, I'm noticing another issue.
Now, if I've selected a cell, the next time the Macro runs, it will select the previous cell as the activecell even if I've selected a different cell.
This was NOT an issue before.


Here's the code.

Sub CellPost() 
    Dim myRow As Long
    Dim val As String
    Dim activeRow As Long    
    val = ActiveCell.Value
    myRow = ActiveCell.Row        
    Sheets("Gunsmoke").Activate
    Sheets("Gunsmoke").Select    
    activeRow = ActiveCell.Row
    Cells(activeRow, 1).Select    
    If ActiveCell.Column <> 1 Then
        MsgBox " Select a Lot Number from Column A "
        Exit Sub
    Else
        If ActiveCell.Interior.Color = vbYellow Then
            MsgBox " This Lot was already Invoiced"
            Exit Sub
        Else
            Sheets("Parts&Labor").Unprotect
            Sheets("Parts&Labor").Range("A18:E22").Locked = False
            Sheets("Parts&Labor").Range("E3").Value = Now()
            ' MORE POSTING IS DONE HERE
            ActiveCell.Interior.Color = vbYellow
            ActiveCell.Offset(0, 8).Value = Now()
            ' MORE POSTING IS DONE HERE
        End If
    End If
End Sub