Mike,

Can you explain how that relates to the formula?
horz pixels == 2 * horz dialog units * (average char width of dialog font
/ average char width of system font)
vert pixels == 2 * vert dialog units * (average char height of dialog font
/ average char height of system font)

I have used fontmetric to get the average width as follows:
lnVal = FONTMETRIC(6,'Tahoma',8) && LnVal = 5 in this case

But I dont know if this values relates to the dialogue font or the system font.