1.) using VBARun at the command line choose to run the "showformnew" macro.
2.)Once the Main dialog is shown select the source layer key style drawing by clicking the "Browse" option from within the "Source" combo dropdown identified by the number 1 in the graphic shown above. Once you browse to a file and choose it, you will be asked whether to open the drawing read only.
3.) Once you have chosen a drawing, click in the Source Layer key Style dropdown identified by the number 2 in the graphic shown above and choose your Source layer Key Style from those provided in the list. (See Graphic for example)
4.) You will now see a popup dialog confirming your selection and directing you to begin selecting your target file and keystyle. This dialog box will dismiss itself after 3 seconds. Repeat the process begun in steps 2 and 3 by choosing from the right side of the main dialog box. Choose your target drawing file by clicking the target drawing file dropdown indicated by the red number four in the first graphic.
5.) Proceed to the last dropdown box and select your target key style from those listed in the key style drop down box indicated by the red number 4 in the first graphic.
6.) Once you have completed the target file and keystyle selection you should see the form stretch to display the missing keys found in the source but not found in the target. (see graphic below.)
7.) All that remains is for you to choose whether to allow overrides, select the keys to be copied, and click the button in the lower right hand corner to complete the task.
Note: This was all done via vba. I have unlocked the macro so feel free to improve the routine. All I ask is that you please email me your improved/debugged copies and let me know what you think of this utility.