Hi @mtr_windows ,
Try to modify the Button12_1 property in MonthDayGallery in AdjustDateScreen as follows.
OnSelect property:
If(DateAdd(firstDayInView, ThisItem.Value) >= Today() && DateAdd(firstDayInView, ThisItem.Value) <= DateAdd(Today(),7,Days),
Select(Parent);
Set(DateSelected, DateAdd(firstDayInView, ThisItem.Value, Days)))
Color property:
If(DateAdd(firstDayInView, ThisItem.Value) < Today() || DateAdd(firstDayInView, ThisItem.Value) > DateAdd(Today(),7,Days), ColorFade(RGBA(47,41,43,1), 80%), RGBA(47,41,43,1))
The sample:

Hope this helps.
Sik