3 external monitors connected to my Laptop Spectre

[BrownSpectre]

Hello I have a Laptop Spectre and 3 external monitors.

I purchased a great split box (Plugable - display link/4K plug and display) that has 3 monitor entries, but when I connect my 3 monitors,

only 2 of them work plus the laptop screen.

So technically I do have 3 screens, except that I would like to replace the laptop screen by the third external monitor when I am connected.

Any idea ?

Thank you

[banhien]

@BrownSpectre 

I don't know what is your great split box. What is the maximum resolution it can drive ? What is the TOTAL resolution of your 4 monitors (including laptop screen).

You can work out the numbers and bear in mind: total resolution number of all monitor can't exceed the maximum the split box can drive.

Regards.

[BrownSpectre]

Thank you @Banhien,

I appreciate that you took the time to answer me.

My problem is not there, my problem is to tell the system somewhere that I do not want to use the laptop screen but an external monitor instead.

If I connect my split box to a desktop, it works -I can use the 3 external monitors).

The display setting shows 3 displays including the laptop built in display, I would like to use an external display instead, so that I could use 3 external monitors.

thank you