Question

I can’t seem to get it to work right

Private Sub Worksheet_SelectionChange(ByVal Target As Range)

Dim LastRow As Long
If Not Intersect(Target, Range("C7,D7,E7,F7,G7,C8,D8,E8,F8,G8,C9,D9,E9,F9,G9,C10,D10,E10,F10,G10,C11,D11,E11,F11,G11")) Is Nothing Then
Application.EnableEvents = False
    With Selection.Borders(xlDiagonalDown)
        .LineStyle = xlContinuous
        .ColorIndex = xlAutomatic
        .TintAndShade = 0
        .Weight = xlThick
        Application.EnableEvents = True
    End With
    With Selection.Borders(xlDiagonalUp)
        .LineStyle = xlContinuous
        .ColorIndex = xlAutomatic
        .TintAndShade = 0
        .Weight = xlThick
   End With
    With Selection.Font
        .ThemeColor = xlThemeColorDark1
        .TintAndShade = -0.249977111117893
    End With
    End If
End Sub

Answer 1

Your code does work (or at least, tell us what doesn’t).

Please be sure to put this code in a Worksheet Module:

• Select the Worksheet where you want the code to get applied
• Right-click on the Worksheet Name
• Click on View Code…
• Paste your code

[EDIT] You should probably reactivate the Events at the end of your code:

Application.EnableEvents = True