Calling A Proc From In A Flag

I was wondering if any one might know what I am doing wrong here or if this is even possible. I am trying to call the testFilePath proc in the -image flag for picture. It runs but does not put the return string into the -image flag.

proc string testFilePath( string $name ) {
string $xtest = ("C:/testdirectory/"+$name);
return $xtest;
print ($xtest+"\n");
}
window testwin;
columnLayout;
string $testpic = picture -image testFilePath("test.bmp");
showWindow testwin;

I know I can stick the result from testFilePath into its own var then just call it at the -image flag, but I would rather not. The interface I am building is very art intensive and it would be a pain to declare each piece of art.

Thanks in advance,
JDA

try:

string $testpic = picture -image (testFilePath("test.bmp"));

Got it! Thanks! I could have sworn I had tried that one but apparently I did not.
Thanks again,
JDA