in reality sysmetric() function gives thes values fo any vfp Horizontal and Vertcial scrollbars:
sysmetric(7) Width of scroll arrows on horizontal scroll bar
sysmetric(8) Height of scroll arrows on horizontal scroll bar
sysmetric(5) Width of scroll arrows on vertical scroll bar
sysmetric(6) Height of scroll arrows on vertical scroll bar
When summing columns and lines of the grid horizontally must add
grid deletemark+recormark widths ( if enabled)

must calculate with these values but it not needs to a big precision here.