Can not use formula with formular column

[leakhna]

every column have formula and I want to calulate another column which is take from that column but it was error.

Example:
Column A: I got data by using this formular IF(COUNTA($I6)>=1,$I6-48,"") and we got data ( 5 Jun)
Column B, row 1: i use this formula IF(COUNTA(A)>=1,A-7,"") it work but row 2 it show this "#VALUE!" unless I have value in column A row 2.

I want column B blank when A column no value and it would be automatic calculate when A column have value.

Thanks you in advance for your guys help.
Leakhna

[sandy666]

=iferror(if(counta(a5)>=1,a5+7,""),"")