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Have you tried using conditional formatting?
If you select all of the columns (or even the entire worksheet), then from the menu select Format/Conditional Formatting...
Change the second box to "equal to" and enter your search text. Then click the Format... button and go to the Patterns tab to set a pleasing color. Click OK and OK and select a single cell from the worksheet. All of the cells that contain the search text should now be displayed in that color.
To search for something else, just select the worksheet again (important!) and click Format/Conditional Formatting... then change the search text.
If you know VBA, the process can be automated.
Hope this helps.