Excel Dynamic Chart from multiple sheets

Hi All,

I am new to excel pivot table/charts. I have to create a Employee Progress Tracker where each employee has a separate worksheet to fill in the Tasks/Actions done by him/her.
The columns(headings) are the same for each employee but the number of rows can differ. I have to create something that enables my Senior Manager to pick from a drop down menu from the Main worksheet and display the information as a bar chart around

Employee (to be selected from a drop down menu listing all the employees)
The date range (can be a free form fields with Start Date and End Date i-e 1/3/2011 to 3/2011).
The Tasks the performed by the employee during the selected date range.
The percentage of the task completed.
Thankyou