This example shows another approach that gives you more control.
Adapted from example given in the Scripting Index entry for Display Boxes > Col Box:
Names Default To Here( 1 );
New Window( "Button in Row",
exx = 1;
exy = 4;
exz = 8;
Table Box(
String Col Box( "strings", {"x", "y", "z"} ),
Number Col Box( "values", {exx, exy, exz} ),
Col Box(
"buttons",
Button Box( "Button 1" ),
Button Box( "Button 2" ),
Button Box( "Button 3" )
)
);
);