impossible to pass a parameter of type 64 bytes in a webservices

[dosreis]

In QTP I execute a webservice logon with parameters key , user and password
The Webservice returns a trunken ( this trunken is a 64Bynari )
QTP reads this trunken in STRing

And i have to pass this trunken in another Webservices with parameters key and trunken

And it is impossible to pass the parameter Trunken
There is an error if i pass the trunken in th from of a string system.xml exception
It is necesary to convert this in 64 bytes or not

How to pass the result of the webservice n° 1 to the following Webservices n°2

Thank you for your help