Make a selection greyscale

Step 1 - Open image and display Script toolbar
If it isn't already open, open the image you wish to modify. Also, make sure the Script toolbar is displayed.
Step 2 - Choose a selection tool
From the Tools toolbar, choose a selection tool appropriate for the image element you wish to select. Your choices are Selection (for standard shape-based selections), Freehand Selection (for irregular shaped selections), and Magic Wand (for selections based on color, brightness, and opacity).
Step 3 - Set tool options
In the Tool Options palette, choose settings for your selection tool.
Step 4 - Make selection on image
Make your selection. A marquee will appear around it.
Step 5 - Apply GreyscaleInPlace script
From the Script toolbar, select and then run the GreyscaleInPlace script -- it's located in Paint Shop Pro's Scripts-Restricted folder. You can choose this script from the Select Script drop-down if your File Locations are set to look in this folder. When applied, the selection will be converted to greyscale.
Step 6 - Turn off the selection
If you haven't already deselected, choose Selections > None to deselect.
Perform this step for me.
Notes and Tips:
To create another interesting effect, after making your selection from Step 4 above, invert the selection (choose Selections > Invert) and then apply the script. This will convert everything else to greyscale while keeping your original selection untouched.
For more information on setting up your File Locations preferences, refer to the Help system or User Guide.

Learn More:
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Modify a photo via blend modes
Add a drop shadow and caption