Distance depending on the value that I to type

I am with a problem in the dynamic text.
I have two dynamic texts fields, I have a function that he goes to catch this value and to put inside of the fields, i alredy do this.
my problem:
I do not know how much the person goes to type, R$ 1,500.00, or R$ 20,54, or USS 256,00. I have two dynamic texts fields one of the side of the other, it is with a distance depending on the value that I to type.
like this, if a put R$ 1.054,32, work fine, but if I put this US$ 12,00, it is thus appearing like this, US$____12,00, e cannot have this distance, the US$ to have that to be together.
it has some skill to count how many characters go to have, when it sees how many he has, it arrive close.

(US$ or R$) dynamic text instance = moeda_txt
(1.200,00 or 562,00) dynamic text instance = inteiro_txt