VBA: Border arond

Try

Sub Catotal1()
    Dim i As Long, j As Long
    With Columns("D")
        i = .Find(What:="Cat*", after:=.Cells(1, 1), LookIn:=xlValues).Row
        j = .Find(What:="Total", SearchOrder:=xlRows, SearchDirection:=xlPrevious, LookIn:=xlValues).Row
    End With
    Range(Cells(i, 4), Cells(j, 4)).Borders.LineStyle = xlContinuous
End Sub

Give this a try:

Sub Macro2()
    Set r1 = Columns("D:D").Find(What:="CAT", After:=Range("D1"), LookIn:=xlFormulas, _
        LookAt:=xlPart, SearchOrder:=xlByRows, SearchDirection:=xlNext, _
        MatchCase:=False, SearchFormat:=False)
        
    Set r2 = Columns("D:D").Find(What:="TOTAL", After:=Range("D1"), LookIn:=xlFormulas, _
        LookAt:=xlPart, SearchOrder:=xlByRows, SearchDirection:=xlNext, _
        MatchCase:=False, SearchFormat:=False)
    Range(r1, r2).Select
    Selection.Borders(xlDiagonalDown).LineStyle = xlNone
    Selection.Borders(xlDiagonalUp).LineStyle = xlNone
    With Selection.Borders(xlEdgeLeft)
        .LineStyle = xlContinuous
        .ColorIndex = 0
        .TintAndShade = 0
        .Weight = xlThin
    End With
    With Selection.Borders(xlEdgeTop)
        .LineStyle = xlContinuous
        .ColorIndex = 0
        .TintAndShade = 0
        .Weight = xlThin
    End With
    With Selection.Borders(xlEdgeBottom)
        .LineStyle = xlContinuous
        .ColorIndex = 0
        .TintAndShade = 0
        .Weight = xlThin
    End With
    With Selection.Borders(xlEdgeRight)
        .LineStyle = xlContinuous
        .ColorIndex = 0
        .TintAndShade = 0
        .Weight = xlThin
    End With
    Selection.Borders(xlInsideVertical).LineStyle = xlNone
    Selection.Borders(xlInsideHorizontal).LineStyle = xlNone
End Sub

You can also do that with conditional formatting. Select Column D and use: =$D1<>"" and specity border...

Assuming that Gary's Student's interpretation that you want an outside border around the whole range (I wasn't sure by your question (and I'm still not)) you can also try

Sub Catotal2()
    Dim i As Long, j As Long
    With Columns("D")
        i = .Find(What:="Cat*", After:=.Cells(1, 1), LookIn:=xlValues).Row
        j = .Find(What:="Total", SearchOrder:=xlRows, SearchDirection:=xlPrevious, LookIn:=xlValues).Row
    End With
    Range(Cells(i, 4), Cells(j, 4)).BorderAround ColorIndex:=3, Weight:=xlThick
End Sub

"Total" in first cell in D and go don't until ""

Are you saying from D1 to last used cell in Column "D"?

Just knocking off for the night but I'll post this until someone comes up with something better

Sub BorderAgain()
    Dim lRow As Long, c As Range
    lRow = Cells(Rows.Count, "D").End(xlUp).Row
    For Each c In Range("D1:D" & lRow)
        If c.Value = "Total" Or c.Value = "total" Then
            Range(c, c.End(xlDown)).BorderAround ColorIndex:=1
        End If
    Next
End Sub