To select a file/folder or to get the full path of a file/folder, You can follow the following the lines in your script :
Send,{ctrl down}c{ctrl up} ;to copy the file/folder path
ClipWait
FileFullPath=%Clipboard% ;stores the clipboard in FileFullPath
SplitPath,FileFullPath, name, dir, ext, name_no_ext, drive
MsgBox, ,Selected file,The selected file is %name%.
Send,{ctrl down}c{ctrl up} ;to copy the file/folder path
ClipWait
FileFullPath=%Clipboard% ;stores the clipboard in FileFullPath
SplitPath,FileFullPath, name, dir, ext, name_no_ext, drive
MsgBox, ,Selected file,The selected file is %name%.