In case this hasn't been said yet, to find a length of a string:
dim("string in quotes" or stringvar)
The response will be a number, the length in character of the string. To
find pixels wide, multiply by 6, as that is the width of each character in
the string.
To put a string at the center of the program screen, use this form:
Output row,119-dim(string),string
Paul DeLeeuw