Spare parts drop down list problem

[lewis63]

Hi
New to this forum & Excel.
i am currently trying to make a customer spare parts quotation but have an issue with selecting "customer" "machine" "serial No." drop down lists. [TABLE="width: 600"]
<tbody>[TR]
[TD]CUSTOMER[/TD]
[TD]MACHINE TYPE[/TD]
[TD]SERIAL No.[/TD]
[/TR]
[TR]
[TD]JOE.BLOGGS[/TD]
[TD]MC TYPE1[/TD]
[TD]1234[/TD]
[/TR]
</tbody>[/TABLE]

My problem is:- we have 4 main "types" of machine, some customers have only 1 machine of 1 type, some have many machines of one type and some up to 3 different types. so how do i get dependent drop down list's to show the choice of up to 4 machine types (if the customer has 3 then show the 3 he has) then once the "type" has been selected. show the serial No.s of all that machine type the customer has.
I have done this with data validation & named cells but as you can't have spaces in the "name" as with the customer name JOE.BLOGGS or JOE_BLOGGS this doesn't look good as an end result.
Would appreciate any help with this as i have been trawling through hundreds of drop down tutorials but none of which suit my dilemma