Need to add to this formula to first check the value in cell(h3) if it is a
credit do not use the formula below and return the value in H3, if the value
is greater than 0 use this formula

=IF($Q$2=($G3+1),IF($Q$2<=($G3+30),$H3,""),"")

Q2 is a user entered date and g3 is the invoice date, H3 is the invoice
amount.