How to create macro with variable number of columns?

Hi, I have created a macro, but it is for a worksheet that has variable number of columns. In the code below, B7 will always be the start cell, but D35, could be E35 and so on, how do I deal with this please?

Range("B7:D35").Select
    Selection.Borders(xlDiagonalDown).LineStyle = xlNone
    Selection.Borders(xlDiagonalUp).LineStyle = xlNone
    With Selection.Borders(xlEdgeLeft)
        .LineStyle = xlContinuous
        .ColorIndex = 0
        .TintAndShade = 0
        .Weight = xlThin