Question : formatting a string in vb.net(urgent)

i was trying to format a string.
lets say a="abc" i want to format it in according to the field mask provided (for example if the field mask is @@###@@ the result is @@abc@@). I dont want to do concatenation operation. is there any way to do this using string.format or any other format function. the format function i used wasn't working for strings. i wrote the following line to print the result
dim a as string="abc"
  MsgBox(Format(a, "@@###@@") 'it showed me @@###@@
 any ideas???
Thanks

Answer : formatting a string in vb.net(urgent)

I think iboutchkine was going for something along the lines of:

Dim s As String
       s = "abc"
       s = String.Format("@@@{0:###}@@@",s)
       MsgBox(s)


Notice the Second parameter to the String.Format