diff --git a/gen_settings.pl b/gen_settings.pl
index d3389b5..2f94e49 100755
--- a/gen_settings.pl
+++ b/gen_settings.pl
@@ -1,4 +1,20 @@
 #!/usr/bin/env perl
+
+#This script replaces MRW attribute names with their values from the
+#MRW XML in any file.  In addition, it can evaluate mathematical
+#expressions if they are in [[ ]]s and can use variables passed in from
+#the command line in those expressions.
+#
+#For example, if the attribute FOO has a value of 50 in the MRW, and
+#the program was started with: -v "MY_VAR1=200 MY_VAR2=400"
+#
+#then the line
+#  [[(MRW_FOO * MY_VAR1) + 5]]..[[MRW_FOO * MY_VAR2]]
+#
+#would get written out as:
+#  10005..20000
+#
+
 use strict;
 use warnings;
 
@@ -6,11 +22,13 @@
 use Getopt::Long; # For parsing command line arguments
 
 # Globals
-my $force           = 0;
+my $force          = 0;
 my $serverwizFile  = "";
-my $debug           = 0;
+my $debug          = 0;
 my $outputFile     = "";
 my $settingsFile   = "";
+my $expressionVars = "";
+my %exprVars;
 
 # Command line argument parsing
 GetOptions(
@@ -18,6 +36,7 @@
 "i=s" => \$serverwizFile,    # string
 "o=s" => \$outputFile,       # string
 "s=s" => \$settingsFile,     # string
+"v=s" => \$expressionVars,   # string
 "d"   => \$debug,
 )
 or printUsage();
@@ -45,6 +64,11 @@
 open(my $inFh, '<', $settingsFile) or die "Could not open file '$settingsFile' $!";
 open(my $outFh, '>', $outputFile) or die "Could not open file '$outputFile' $!";
 
+if (length($expressionVars) > 0)
+{
+    loadVars($expressionVars);
+}
+
 # Process all the targets in the XML
 foreach my $target (sort keys %{$targetObj->getAllTargets()})
 {
@@ -67,16 +91,41 @@
     close $outFh;
 }
 
+#Parse the variable=value string passed in from the
+#command line and load it into %exprVars.
+sub loadVars
+{
+    my $varString = shift;
+
+    #Example: "VAR1=VALUE1 VAR2=VALUE2"
+    my @entries = split(' ', $varString);
+
+    for my $entry (@entries)
+    {
+        my ($var, $value) = $entry =~ /(.+)=(.+)/;
+
+        if ((not defined $var) || (not defined $value))
+        {
+            die "Could not parse expression variable string $varString\n";
+        }
+
+        $exprVars{$var} = $value;
+    }
+}
+
 # Usage
 sub printUsage
 {
     print "
-    $0 -i [XML filename] -s [Settings YAML] -o [Output filename] [OPTIONS]
+    $0 -i [XML filename] -s [Settings YAML] -o [Output filename] -v [expr vars] [OPTIONS]
 
 Required:
     -i = MRW XML filename
     -s = The Setting YAML with MRW variables in MRW_<MRW variable name> format
     -o = YAML output filename
+Optional:
+    -v = Variables and values for any [[expression]] evaluation
+         in the form: \"VAR1=VALUE1 VAR2=VALUE2\"
 Options:
     -f = force output file creation even when errors
     -d = debug mode