Addition of positive numbers of selected cells

[Agridoc]

Could anyone please tell me how to add only positive integers in selected cells in a row or column. Eg.
A. B. C. D. E. F. G. H. I. J. K. L. M. N. O. P. Q.
1. -2. 3. -4. 5. 6. 7. 8 7 -3. 2. -4 1. 8. -6. 8. 3

I want to add cells D, H, L and P, ie -4 + 8+ -4 +8 I want the sum of only positive numbers.

 

[arthurbr]

Hello
how will the cells be selected?

 

[Agridoc]

Hello
how will the cells be selected?

Thank you for the response...I got the formula ...it's =Sumif(cellA:cellA,">0")+sumif(cellB:cellB,">0"+....