Using lookup function that locates the nearest lowest AND greatest value?

Hello,

I'm trying to solve this bit of function problem.

I'm trying to use vlookup function in table 2 referencing table 1 using the approximate parameter. However, an approximate vlookup value is by definition the closest *least* value. Is there a trigger of some sort to locate the closest *greatest* value as well?

For instance, if the lookup_value in table 2 is 2.450 but the referenced table 1 only has 2.445 and 2.475, I will only retrieve the respective value related to 2.445 -- how would I retrieve the other value at 2.475?

Essentially, if a lookup_value rests in between two values of whatever is being referenced, I am trying to average those two closest numbers. Is there a function I've overlooked that may help with this?

Thanks...