To sum only positive values in Excel, you can use the SUMIF function. This function allows you to specify a criteria, and then sum only the cells that meet that criteria. In this case, the criteria would be "greater than 0".

Here's an example of how to use the SUMIF function:

=SUMIF(A1:A10,">0")

This will sum all values in the range A1:A10 that are greater than 0. You can change the range to whatever cells you want to sum.