For the first part I think you'd need VBA, not really my area of expertise but I'm sure somebody else can point you in the right direction......

For the second part you could use the WORKDAY function which excludes weekends, i.e. in C1

=IF(WORKDAY(B1,A1)<TODAY(),"Not OK","OK")

Note: Workday function is aprt of Analysis ToolPak add-in. If you don't have that installed try:

Tools > Add-ins > Tick "Analysis ToolPak" box