Dynamically adjust data range to an excel chart

Hi have an workbook "Main" where I show a graph .On this workbook I have a cell A1, "Company Name" which refers to data on a sub workbook.

Worksheet 1 : Main (where the graph is)
Worksheet 2 : Company 1
Worksheet 3 : Company 2
Worksheet 4 : Company 3

On Workbook 1, I want to enter Company 1 in cell A1 and dynamically draw a graph from a data range on Worksheet 2 : Company 1. If I change A1 to Company 2, the graph data range should be from Worksheet 3 : Company 2.

How do I handle dynamic data ranges?