Finding Height

Hi,
In my code i using like this:

float height = 0.0;
text = “OpenGL”;
for (unsigned int loop=0;loop<(strlen(text));loop++)
{
height+= gmf[text[loop]].gmfCellIncY;
}
When i am getting the height value it is always zero. But i am getting the length.
How i can get the height?.

Thanks
Kannan