Data Validation and Filter help

Hello all, 

I am having trouble with data validation. 

I am working in a workbook for timesheets,  I have on sheet one called MasterSheet, several lists.  Column A is Companies,  Column B,C,D,E List Leases for each of the companies in Column A.

 What I am trying to accomplish is:

On another sheet labeled Monday. In cell G20 I have a dropdown list,  that is data validated to Column a on MasterSheet, (Companies)

I have currently 6 companies in the list.  In Cell G20 I have another dropdown list.  

When I select say Company B in the list i need the lease list in G20 to reflect the Lease list for Company B Which is in column E1:E30 which is on the MasterSheet

Any help would be great