Transpose and Merge Variables into a Single Column

Does anyone have a good way to transpose and merge multiple columns into one, while inserting a new column that identifies each transposed record with the corresponding column header, and copies down the non-transposed columns to the left of the transposed variables so they line up with the transposed variables?

Please see the attached file for further clarification on what I am looking for...

I would like variables X,Y, and Z on the 'Input' sheet transposed and merged into one column, an additional column inserted to identify each transposed value, and the values of the columns not being transposed copied down, as shown on the 'Output' sheet.

The number of variables being transposed may change, so I'd like the macro to work based on how many columns are highlighted. The number columns that are being copied can be consistent (first two or three columns on the sheet).

If anyone has any ideas, that would be great!

Thanks!