String.Format: join two value in one padding

How can I do something like

string.Format("({{0}{1},10})","ABC","DEF) // (    ABCDEF)
string.Format("({{0}{1},10})", "ABC", "DEF)// (   ABC DEF)

I have to solve tihs operation with format. And I do not have a chance to combine elsewhere.

So is not it possible to do something like.

Console.WriteLine(string.Format("({0,10})","ABC"+" DEF"));

I cant use join or concat or a + b methods

Why i want only format pattern? Because of usage like this.

//Dummy metod for examplepublicstaticstring applyFormat(String format,String values,Objectobject){
    member1 = reflect fromobjectby named extracted string
    member2 = reflect fromobjectby named extracted stringor members[]= exploded stringreturnString.Format(format, member1, member2);orreturnString.Format(format, members);}
Usage Example
Console.WriteLine(applyFormat("({ {0}{1},-10})","Member1,Member2",object));// "({ {0}{1},-10})": Reflect and Join Member1 and Member2 and apply padding joined value