IF condition in Data Validation

Is it possible to combine an IF condition in Data Validation?

Dear Forum,

I am trying to combine the Functionality of a List in Data validation and an Independent Single value if a particular condition's not met..

It goes like this...?

I have three Options of Investment :
1. Option_I
2. Option_II
3. Option_III


I want 2 conditions working based on the three selections, like if the USER selects the Option_I then it should display "Actual Dates" and for anything other than "Option_I" it should provide a list as below:

1. 12 MOnths
2. 13 MOnths
3. 14 MOnths
4. 15 MOnths
5. 16 MOnths
6. 17 MOnths
7. 18 MOnths. --This LIst is Name Defined as AdvancePlanning

Actually, I tried using the formula but in vain:

[ = if($B$12="Option_I","Fixed Dates",AdvancePlanning)  ]

It does not work...

Am I making a mistake somewhere? or its not possible?

Warm Regards
e4excel