Can I create a TYPE (or DOMAIN) with arguments?

Hello,

I'm trying to create a composite type with an argument, to create one field of this type like character varying(x), but
Idon't know if this can be done with PostgreSQL. I want something like: 
CREATE TYPE mytype AS (
    tx       character varying(x),
    t2nd       integer
);
I need to limit the number of chars in this field tx. And different lengths will be used when creating tables with this
type(so a Domain will suffer the same problem). I'm not looking for a solution like a separate column with maxChars and
aCheck, because lots of columns will be required (and others design reasons). 

Any suggestions?

Thanks.

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