[AccessD] Validation of a control

I am not managing to get this right despite numerous attempts. Let's call
the controls C1, C2 and C3. C1 is a combo which contains 5 columns. The
first is its ID, the second and third are the min and max values permitted
in C2. The fourth and fifth are the min and max values permitted in C3.

Perhaps because I am using some fancy code inherited from Gustav and Shamil,
I seem to have lost control over the BeforeUpdate event, so I am leaning
toward the Validation attributes instead. Let's suppose that the item
selected in C1 contains 100, 120 in columns 2 and 3 and 500, 700 in columns
4 and 5. Once the user has selected one such row in the combo C1, how do I
rewrite the validation statements for C2 and C3?

TIA,
Arthur