Hi Webmax,
Below are the recommendations:
If the numbers are always postive then try:
=SUMIF(B2:E2,">0",B2:E2)
If the numbers can be +ve or -ve try:
=SUM(IF(ISNUMBER(B2:E2),B2:E2))
Note this will be array formula; so must be entered with Ctrl+Shift+Enter
If you are using Excel 2010 or Excel 2013 then you can also try:
=AGGREGATE(9,6,B2:E2)
Regards,