i have recently been attempting to write a small text editor application, and the main problem i found was migrating notepad settings over to my application, the font for 10pt was stored as 100.
obviously, i needed to divide by 10, but when i did this, the font came out so small it was unreadable.
after some digging, i found the following works perfectly.
int m_height = -MulDiv(g_point_size/10, GetDeviceCaps(m_dc, LOGPIXELSY), 72);
once you have done this, just SendMessage to the EDIT you want to set the font size of, and bingo, we have a correct font size