Hi Craig,

Will this work"?

In Duration & Defect!D4...

=IF(AND(ISNUMBER(Master!$K$5),ISNUMBER(Master!$T$5 )),Master!$K$5+Master!$T$5,"")


In Duration & Defect!H4...

=IF(AND(ISNUMBER(Master!$L$5),ISNUMBER(Master!$U$5 )),Master!$L$5+Master!$U$5,"")


In Duration & Defect!J4...

=IF(AND(ISNUMBER(Master!$K$5),NOT(ISNUMBER(Master! $T$5))),Master!$K$5,"")

In Duration & Defect!N4...

=IF(AND(ISNUMBER(Master!$L$5),NOT(ISNUMBER(Master! $U$5))),Master!$L$5,"")

In Duration & Defect!P4...

=IF(AND(NOT(ISNUMBER(Master!$K$5)),ISNUMBER(Master !$T$5)),Master!$T$5,"")

In Duration & Defect!T4...

=IF(AND(NOT(ISNUMBER(Master!$K$5)),ISNUMBER(Master !$T$5)),Master!$U$5,"")


Hope I didn't stuff-up anywhere, it wasn't easy keeping track of what
goes where!

Ken Johnson