Empty Cell Versus Null

How exactly does Excell treats uninitialized variables ? I have created a function which takes in one of the cell values as a parameter.. However, it seems that when I don't reference an empty cell, the code does not work. Let the function be ABC, and the let the cell be A1

When I use
=ABC(....,A1,....) , it works
However, when I use
=ABC(....,,....) I am getting an eror

Now , I tried using the IsEmpty function , and it seems tht when i use ,, or ,"", then the variable is not caught.. however, the variable is caught when i use an empty cell such as ,A1,

FYI, I am using the vba's formula method to assign this function to a cell. So when I use
"," & ActiveCell.Offset(to reach A1).Value & "," , I see blank ,, when A1 is empty