Limit values in a list box

[#1]

I have a list box that contains values for the type of results. The values are B,L, UA, W, TRF. I would like to exclude the value B and not allow it to be selected. Does this have to be done in an expression, and if so what would the formula look like?

Thank you for any help.

[#2]

if(Value<>'B', Value)

[#3]

Perfect - and way too simple.

[prabhu0505]

very useful