Access Dynamic path/folder with ios:ofstream

For Making long description short see my case:

Code:

suppose,

path: "../defult123/test.txt"

my code: ofstream fout("../defult123/test.txt",ios::out);

Here in "defult123", "default" is static but "123" is dynamic .So Basically 

path should be written as: "../default***/test.txt"

So how can i access this dynamic path for writing in test.txt file.

Code:

so should be working ??
ofstream fout("../default*/test.txt") 

or,do  i have to list directory fist then check for folder named "default" in sub folder? if so then how do i do that?

please be a help....