using a verable in a string with out a space

[nathan-whitehouse-2]

This one should be easy and I should be able to find it online but I must not be asking the google machine the right question.
I need to use a verable as part of a file name nested in another verable.
Simply put I need to set a verable that points to a file name. And that file name I need to pull its verable from a param passed via the cmd line.
Looks something like this

Param([Parameter(Mandatory=$true)][String]$a1
$Filename ="D:\Folder\$a1 File.txt"

I need to remove the spacein the file name.

As always Thanks!!!

[system]

You can place the variable name in curly braces to help the parser figure out which part is the variable, and which is the string after it:

"${a1}File.txt"

You can also use the subexpression operator, but I prefer the first option instead. You can see why when you look at this code in the ISE; the syntax highlighting is nice and neat with the braced variable names.

"$($a1)File.txt"

[nathan-whitehouse-2]

Perfact!!!

Thanks