how to execute the command after change ppp user&pass ?

[‫mahmoud helmy‬ ‫]

hello sirhow to execute the command after change ppp user&pass ?
because if I from preset-Configurations set to change WANPPPConnection.3 ppp user name (for example),and another set to change its ppp password, in the same preset , 
the problem : it lost the connection after change  ppp user name, (before change ppp password ) ,so I want to execute the command after change ppp (user&pass) together , 

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