Adding row when data is entered

I have a spreadsheet that I am needing to add two rows to when a certain cell
has data entered.

Example
A B C D
1 xx xx xx Data entered here
2 Blank row
3 This is where I want to add two rows on the data has been entered in D1.
4 Blank row
5 Once again I want two rows once data is entered into D3 and so on ending
at a specified row since this form has several heading that this will apply
to.