View criteria

Hi,

I don�t know how to make this:
I have 2 forms:

Form1:
IDCLIENT
FIELD1
FIELD2
FIELD3

Form2:
IDCLIENT (Lookup from the Form1)
FIELD4
FIELD5
FIELD6

Now I want make a view with the IDCLIENTS of the Form1 not present in the Form2.

Thanks in advance.

Regards