Syntax for formatting a number with a comma for thousands

I'm using this code to add a column total, what do I need to add to centre the number in the cell and to format it using a comma for thousands?

        LastRow = Range("D65536").End(xlUp).Offset(2, 0).Row
        Range("D" & LastRow) = "=Sum(D1:D" & LastRow - 1 & ")"
        Range("D" & LastRow).Font.Bold = True
        Range("C" & LastRow) = "Total"
        Range("C" & LastRow).Font.Bold = True

Many thanks