The TBM_SETPAGESIZE message sets the size of the page for a trackbar. The page size affects how much the slider moves for the TB_PAGEUP and TB_PAGEDOWN notification messages.
TBM_SETPAGESIZE
wParam = 0;
lParam = (LONG) lPageSize;
Parameters
lPageSize
New page size.
Return Values
Returns a 32-bit value that specifies the previous page size.