Enabling A Command Button - Help With Code

I have two text boxes and a check box - so the user can enter (1) patient weight, (2) patient height and then check whether the patient is male or female. The first two are then used to calculate a Body Mass Index. (simple enough and works OK). What I then want to do is have four command buttons that become visible when the calculation is within a certain range. So - simplistically- if the calculation (calctxtbox) is between 0 and 5 AND the patient is female then the command button called "normal"(Command79) is enabled.
My VB code writing is improving (thanks largely to this forum!) but still very basic - can some-one help please?

Do I put my code in the "after update" event of the calctxtbox?

Private Sub calctxtbox_AfterUpdate()
If calctxtbox > 0 (How do I say and <5) and then how do I say Female =Yes Then
Command79.Enabled = True
End Sub
Am I close?
Also can you enable labels and text boxes or just buttons.