Need some help with a CString

I would like to build  a CString like the following:

I want to fill the string with 2 numbers  1)doulbe  2)int
The string should always be 8 bytes long

I also want to fill the 4-6 bytes with " x "


CString A="1.50 x 1500"
                           or
                   "5.00 x   100"
                   "0.55 x     10"
                   "0.01 x   500"
                             |
length=8      012345678

In my old days with business basic I had a function like this one:
int y=200;
Y$ =  y using "####"

double d=0.55
D$ = d using  "##.##"
So I can easly build a String like this "0.55 x  200"          String =  D$+" x "+Y$
                                                                   012345678
     
Is there anything in C++ that I can easy build a string with numbers?
So the string is trimed right?

Please let me know, thanks.
500 points.
Best regards,
Thomas