macro that automatically adds rows with in a specified range

[ca123]

Sir,

I want a macro code which automatically adds one row with in a specified range (E4 : E20) when the number of empty rows in the above said range comes to 3. further, also the formula from above row should be automatically get copied into the newly inserted row across all the columns.

Thanks

[ca123]

i have changed the title of my post to a meaningful one. please get me the macro code I want. thanks in advance