Calibration Dates -

I have a 3 text boxes in my program, One textbox named txtLast, I assign a date. And in txtCal I put in any number and when I click on txtLast it gives me the date plus the number of weeks in txtNext.

It is a calibration program. I need to know when the gauge was last calibrated and when it needs calibrating again. It woks very good except that it will always give me todays date in txtLast. For instance if the the gauge was calibrated last week I need to put in that date, but it returns todays date all the time, this my code:

Private Sub txtLast_Change()
Print Format$(Now, "m/d/yy")
txtNext.Text = DateAdd("ww", Val(txtCal.Text), Date)
End Sub

Private Sub txtLast_Click()
Print Format$(Now, "m/d/yy")
txtLast.Text = Date
txtNext.Text = DateAdd("ww", Val(txtCal.Text), Date)
End Sub

I know Now will give today always, what other can I put in to achieve what I want?

Thanking you all.

Regards