Last Appearing Data In A Sheet

I have a timesheet from which i need to calculate the number of hours put in by employees on a weekly basis.The timesheet can vary with months and number of employees can also change.

Part of code is below:

Dim i As Integer
Dim j As Integer
Dim c2 As Range

Dim startday As Integer
Dim tempnd As Double
Dim tempdys As Double
Dim weekndsum As Double
Dim weekdysum As Double
Dim store_date As Date
m = 12

store_date = thisDate
For i = 20 To 400 Step 5 "value hardcoded

In this i have hardcoded the value,I need it search auto and run till the last used cell.It should replace the number 400 {in my code above}with the last row used.