Combination Chart set to line or bar depending on Series value


let´s assume i have serialiazed my Combination Chart by 'Car'-'Number' variables.

Imagine i have this values in the series:

Car- Number

A     1

A     2

A     3

B     1

B     2




I want that all the rows which have A or (empty) as Car value are draw as a line. If they have B are draw as a bar.

I assume this will relate some kind of script, but take in account i am totally new to that, so please, explain it to me as detailed as posible.