Define My Dynamic Range Start Cell by Input box

The code below was modified to allow you to input a cell address from which to start a selection which extends as far down as there are data in the specified cell's column and as far to the right as there are data in the same cell's row.

Sub DynamicRange()
    ' select the used range to the right and bottom of the sheet
    ' starting from the given StartCell

    Dim LastRow As Long
    Dim LastColumn As Long
    Dim StartCell As String

    StartCell = InputBox("Enter coordinates for determining the used range:", _
                         "Start cell address", "A1")
    With Worksheets("Sheet1")
        'Find Last Row and Column
        LastRow = .Cells(.Rows.Count, Range(StartCell).Column).End(xlUp).Row
        LastColumn = .Cells(Range(StartCell).Row, .Columns.Count).End(xlToLeft).Column

        'Select Range
        .Range(.Range(StartCell), .Cells(LastRow, LastColumn)).Select
    End With
End Sub

I think this is a cumbersome process. Therefore I offer an alternative. Instead of entering a cell addresss, select the cell the address of which you would have entered. The run the code below and the same range will be selected.

Sub DynamicRange2()
    ' select the used range to the right and bottom of the sheet
    ' starting from the selected StartCell

    Dim LastRow As Long
    Dim LastColumn As Long

    With ActiveSheet
        'Find Last Row and Column
        LastRow = .Cells(.Rows.Count, ActiveCell.Column).End(xlUp).Row
        LastColumn = .Cells(ActiveCell.Row, .Columns.Count).End(xlToLeft).Column

        'Select Range
        .Range(ActiveCell, .Cells(LastRow, LastColumn)).Select
    End With
End Sub