AutoCAD 2010 :: Ribbon Combo Box - Text Height

When creating Mtext, I can't figure out how to specify a given height using the ribbon. Clicking on the "A" on the "Home" tab brings up the "Text Editor" ribbon and displays the Mtext editor in the drawing area. On the "Style" panel of the Text Editor ribbon is a drop-down box with a default height of 1/8". Clicking on this drop-down box gives the list, 1/8", 1/4", 1'-6", 1/8", and 3/16". It appears those are my only choices, but I need to make Mtext that is 1'-0" high. If I try to highlight the size selected in the drop-down box and type in 1'-0", AutoCAD erases my typing, replacing it with the 1'-6" choice (or some other member of the preset list). It does this whether or not I have typed text in the Mtext editor, highlighted that text, etc.

If I hover the mouse over the drop-down box, a tooltip comes up that says "Ribbon Combo Box - Text Height / Press F1 for more help." Pressing F1 brings up the Autodesk Exchange window which is blank except for a spinning wheel animation in the center that never stops. The promised "help" never appears.

Right now my only workaround is to create Mtext using one of the heights that AutoCAD has chosen to make available, then select it and change its height using the Properties palette, which may or may not be so easy depending on whether the height I need is very different from the height I was forced to use and the zoom factor of my view (the created mtext might show up as an almost invisible dot, forcing me to play "Where's Waldo" to select it). This is an almost unusable kluge. How can I set the size when creating the Mtext, not afterwards? How is the list of sizes available in the drop-down box determined?