Since FileLocator Pro can accept parameters in the form of a link to a text file you can export your keyword hits from the first search and reimport them for a second search.
To do this as a batch process you'd run something like this:
Stage 1: Search for all 4 digit numbers and save them in a file called FirstStageKeywords.txt
flpsearch.exe -d "C:\Program Files\Mythicsoft" -f "*.txt" -c "\b[0-9]{4}\b" -cex -o "e:\FirstStageKeywords.txt" -ofxslt "C:\Program Files\Mythicsoft\FileLocator Pro\Sample Transforms\unique_hits_only.xsl"
Stage 2: Search for all numbers in the file FirstStageKeywords.txt populated in Stage 1
flpsearch.exe -d "C:\Different\Location" -f "*.txt" -c "=e:\FirstStageKeywords.txt"
More information
You can do the same thing in the FileLocator Pro GUI using either the same XSLT custom format or the Keywords by File Report to generate the keywords for use in the second search.
