Limit values of a combo box based on the value of another field

[WatsonDyar]

Field B is a combo with the options of : 100% Availability, 75% Availability, 50% Availability, 25% Availability, OR Not Available

If I choose "Present" in Field A, I want the "Not Available" value to disappear as an option.

Any ideas?

 

[WatsonDyar]

Thanks UG! I'll check this out now...