This message requests vertical scrolling to the position relative to the total size of the table. wParam contains number of completely visible lines in the window (1 if data area is smaller than 1 line). lParam contains new scrolling position in 1.0/MAXTRACK parts of the total height of the table.
Standard table window should simply pass this message to Tablefunction.
If custom table window supports byte scrolling, it must make line with index (total number of lines)*lParam/MAXTRACK topmost visible in the window. If byte scrolling is not supported, it must be line (total number of lines-wParam)*lParam/MAXTRACK. Window is not allowed to either redraw or invalidate the window. If window's appearance remains unchanged, window function must return -1. If window supports byte scrolling, it must return (topmost line)*MAXTRACK/(total number of lines). If total number of lines is less than or equal to wParam, it returns 0. Otherwise, it must return (topmost line)*MAXTRACK/(total number of lines-wParam). As constant MAXTRACK is relatively big, use MulDiv to calculate return value.