How do I use checkboxes in an IF-THEN statement in Excel VBA 2010?

I need to use the value of checkboxes for an IF-THEN statement. Based on what the user checks, the way I have to calculate things changes. However, I can't figure out how to use the checkbox values, or how to detect them. Here is the code I have so far:

Private Sub Workbook_Open()
    Range("E1:F7,A1:A4,B1:B4,C1:C3").Select
    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
    With Selection.Borders(xlInsideVertical)
        .LineStyle = xlContinuous
        .ColorIndex = 0
        .TintAndShade = 0
        .Weight = xlThin
    End With
    With Selection.Borders(xlInsideHorizontal)
        .LineStyle = xlContinuous
        .ColorIndex = 0
        .TintAndShade = 0
        .Weight = xlThin
    End With
    Range("A1").Select
    Range("A1") = "Time"
    Range("B1") = "Specimen Shape"
    Range("C1") = "Data Type"
    Range("A1:C1").Font.Bold = True
    Range("E1") = "Owner"
    Range("E2") = "Experiment Date"
    Range("E3") = "Specimen ID"
    Range("E4") = "Contaminant"
    Range("E5") = "Leachant"
    Range("E6") = "Temperature"
    Range("E7") = "Regression Title"
    Range("E1:E7").Font.Bold = True
    Columns("A:E").EntireColumn.EntireColumn.Autofit
    'Formatting Column A
    Columns("A").EntireColumn.ColumnWidth = 9.71
    ActiveSheet.CheckBoxes.Add(4, 14.5, 72, 17.25).Select
    Selection.Characters.Text = "Days"
    Range("A6").Select
    ActiveSheet.C