I have a row of values that contains dates and numeric values. I want to SUM all of the numeric values within this row but am having problems figuring out how to do this.

I have tried several array formulas, such as {=SUMIF(K17:CC17,isnum(K17:CC17),K17:CC17)} where "isnum" is a VBA function that uses IsNumeric to determine if a cell contains a numeric value (will, according to Excel Help, return FALSE if the cell contains a date value).

I have tried using the built-in function ISNUMBER but that seems to return TRUE when the cell contains a date, so that's of no help.

I am using Excel 2010.

Thanks.

Function isnum(rng As Range) As Boolean
isnum = IsNumeric(rng)
End Function