yes, do it also to the rest of your control's after update (if you have, ie H, L, W).
wait, you cant do arithmetics with string:
Me.WEIGHT = IIf([WEIGHT CALC] <> "0", ([H] * [W] * [L] * [WEIGHT CALC] / 1000000000), "-")
should be:
Me.WEIGHT = IIf([WEIGHT CALC] <> 0, ([H] * [W] * [L] * [WEIGHT CALC] / 1000000000), "-")
or:
Me.WEIGHT = IIf(Val([WEIGHT CALC] & "")<> 0, ([H] * [W] * [L] * [WEIGHT CALC] / 1000000000), "-")