How to have a drop down selection list

[John]

I am working on project assignment workbook. I have a PROJECT
worksheet that define project and task, I will get the data from
project managers about the hours per week for the each of the project
tasks. So the worksheet structure like below:

Project Name | Task Name | Jan-12 (hr)|Feb-12(hr)|Mar-20(hr)
-----------------------------------------------------------------------------------
Proj-A1000 | App Dev | 160 | 160 | 80
Proj-A1000 | App Test | 40 | 80 |100
Proj-B1011 | Test | 80 | 80 | 40


Then I want to have a worksheet to assign a person to a project task
and then inherit hours. So the TASK ASSIGNMENT worksheet has the
structure like this:

Resource Name |Project Name | Task Name | Jan-12 (hr)|Feb-12(hr)|
Mar-20(hr)
-----------------------------------------------------------------------------------
James |Proj-A1000 | App Dev | 160 |
160 | 80
Paul |Proj-B1011 | Test | 80
| 80 | 40


I know how to use list validation for the Project Name column on TASK
ASSIGNMENT worksheet using Excel 2010 Data Validation feature to
create Project Name list based on the value from PROJECT worksheet.
But I don't how to create TASK list for the Task Name column on TASK
ASSIGNMENT column as the list values will have to based on which
project is selected.

Can experts on this group provide a direction?

Thanks,

John