blanks with formula

Hi I am new to the forum
I want to calculate (A2-A1)/56
sometimes A1 is blank and sometimes A2 is blank if this is the case then I want the formula to ignore that row and give me a blank rather than give me a value.
I tried using an IF and an OR but I keep getting an error message and I'm not sure where I am going wrong
any help with this would be greatly appreciated
Thanks

I suggest using COUNT function to count the numbers in those cells and only proceed with the calculation if there are 2 numbers present, i.e.

=IF(COUNT(A1,A2)=2,(A2-A1)/56,"")