How To Adjust Time Calculations (Total Overall Hours)

In some text boxes I enter times like "08:00 16:00" then another textbox next to it will display 8 hours then a label at the bottom calculates the total overall hours. There are a total of 7 textboxes for times entered and like the example above and another 7 for the calculation of that days hours worked. My problem is when I enter "08:00 16:30" the total hours in that text box would be displayed "8.5 hours". I need to tweak this so it is displayed 8 1/2 hours. My second issue is that the label that displays the overall hours only calculates if I enter times like "08:00 16:00" if i entered "08:00 16:30" it would not calculate

Here is my code:
vb
Private Sub txtMondatTimeKeeping_TextChanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles txtMondayTimeKeeping.TextChanged, _
txtTuesdaysTimeKeeping.TextChanged, txtWednesdaysTimeKeeping.TextChanged, txtThursdaysTimeKeeping.TextChanged, txtFridayTimeKeeping.TextChanged, _
txtSaturdaysTimeKeeping.TextChanged, txtSundaysTimeKeeping.TextChanged
CalculateHours()
[Code] .....