Input Boxes

[A real begineer]

I am trying to run the following code in a case select BeforeUpdate. I keep getting an error mewssage saying I must save the record before I do this. I thought this modified the record before it was saved. I am confused.
strA = InputBox("Free Available Chlorine appears to be high. Please retest to confirm.", "High FAC")
FreeAvailableChlorine.Text = strA

 

[Richie]

Is it on the Form before update, or the control?

 

[A real begineer]

The control before update