Message requests table window to change selection to single-line, move selection up or down by lParam lines and scroll window so that selection is still visible. Special lParam values of MOVETOP and MOVEBOTTOM move selection directly to first or last line in the table. wParam contains number of completely visible lines in the window (1 if data area is smaller than 1 line).
If window does not support single-line selection, it must scroll by specified number of lines.
Standard table window (which anyway does not allow multiline selection) should simply pass this message to Tablefunction.
Custom table window must modify data but neither redraw nor invalidate the window. If position of data remains unchanged, window's 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.