Countif formula for n number of rows and columns in macros vba

hi ,

currently i am working n a excel sheet , i need to include an countif formula column after the last column. and the formula should be pasted till the last value in the row.

ex: if three columns are there then count if column should be inserted in d column. Columns counts are varying and also rows count. Countif function to sum the "X" count .

A B C Count if
1 a x 1
2 x x 2
x x x 3

The number of rows are varying. In some some sheets more rows are coming. i am unable to write the macros.

Kindly help me.