dependent combo boxes

hi,
Need help on the following,

My work book has 4 cols (Name, Vendor, Product, Sub Product)

User Form 1 has 4 combo boxes with same above col names.

I need a code that does the foll;

- When Combo Box ‘Name’ is selected - should list the following ‘Unique’ Values from Col 'Name'
‘Sales Man 1’ & ‘Sales Man 2’

- if ‘Sales Man 1’ is selected in Combo Box ‘Name’,
Combo Box ‘Vendor’ - should list the following ‘Unique’ Values from col 'vendor'
‘Vendor 1’ & ‘Vendor 2’

- if ‘Vendor 1’ is selected in Combo Box ‘Vendor’,
Combo Box ‘Product’ - should list the following ‘Unique’ Values from col 'Product'
‘Product 1’ & ‘Product 2’

- if ‘Product 1is selected in Combo Box ‘Product’,
Combo Box ‘Sub Product’ - should list the following ‘Unique’ Values from col 'Sub Product
‘SP 1.1’ , ‘SP 1.2’, ‘SP 1.3’

Thanks
R