Hello, I struggle incorporating @IF formulas.

I have three date columns. I need to find the work days between any two
dates.

My challenge is when I use the following formula for the following dates:

K5 reflects 01/09/2009 and J5 reflects 01/09/2009 and I5 reflects 01/02/2009

I use the formula =NETWORKDAYS(J5,K5) the value comes to 1 and it should be
zero.

I use the formula =NETWORKDAYS(I5,K5) the value comes to 6 and should be 5

Also another challenge I can't figure out:

K6 reflects 01/12/2009 and J5 reflects 01/13/2009
I use the formula =NETWORKDAYS(I5,K5) the value comes to (2) and should be
(1).

Thank you in advance for your help!!