diff --git a/models/subscript/subscript.dat b/models/subscript/subscript.dat
index 6e37f009..3952cc77 100644
--- a/models/subscript/subscript.dat
+++ b/models/subscript/subscript.dat
@@ -185,3 +185,30 @@ v[A2]
 v[A3]
 0	0
 1	0
+w[X1,Y1]
+0	0
+1	0
+w[X1,Y2]
+0	-1
+1	-1
+w[X1,Y3]
+0	-2
+1	-2
+w[X2,Y1]
+0	1
+1	1
+w[X2,Y2]
+0	0
+1	0
+w[X2,Y3]
+0	-1
+1	-1
+w[X3,Y1]
+0	2
+1	2
+w[X3,Y2]
+0	1
+1	1
+w[X3,Y3]
+0	0
+1	0
diff --git a/models/subscript/subscript.mdl b/models/subscript/subscript.mdl
index 17ff1f75..5124d15d 100755
--- a/models/subscript/subscript.mdl
+++ b/models/subscript/subscript.mdl
@@ -59,6 +59,14 @@ v[DimA] = IF THEN ELSE (DimA = A2, 1, 0)
   ~:SUPPLEMENTARY
 	|
 
+DimX: (X1-X3) ~~|
+DimY: (Y1-Y3) ~~|
+w[DimX,DimY] = DimX - DimY
+	~
+	~	dimensions used in expression position (where expression result can go negative)
+  ~:SUPPLEMENTARY
+	|
+
 ********************************************************
 	.Control
 ********************************************************~