Allowing User To Switch From Metric To Imperial When Ok Button Pressed

I am making a program that calculates various results with variables entered by the user. What I am trying to do is incorporate a function that will allow the user to switch from metric to imperial easily but only when the ok button is pressed. Now I got all the coding done for the metric and everything is working fine. My problem is when I use the radiobuttons to switch the entered variable in the text box to the desired unit it gives me a 0 or a random number in the textbox...

I also have labels indicating each variables unit which I easily managed to change with the text box using this code. :
'Change Labels to Metric
lblMDegreeC.Text = "Degree C"
lblMDegreeC2.Text = "Degree C"
lblMmm.Text = "mm"
lblMmm1.Text = "mm"
lblMmm2.Text = "mm"
lblMm.Text = "m"
lblMm2.Text = "m"
lblMm3.Text = "m"
lblMDegreeC3.Text = "Degree C"

I created all the coding to convert the metric variables to imperial. My problem is changing the textbox text when the user switches the units during run time. The labels change without a problem but the textbox never works. I have attached the coding for the file.