I have a spreadsheet with 2 workbooks called clients and jobs. In the
clients workbook I have 4 columns which include firstname, lastname,
telephone and email.

In the second worksheet (Jobs) I have several columns but 4 are the same as
the ones above the difference being that in the telephone and email columns
I have a formula which populates these cells from the client worksheet using
the first and last name cells. The formula I use (for the telephone column)
is :-

=INDEX(Clients!$C$3:$C$1000,MATCH($K1&$L1,Clients! $A$3:$A$1000&Clients!$B$3:$B$1000,0))

This works fine except I get a #N/A error which I haven't completed the
firstname and lastname cells. I amended the formula to the following to
"hide" the error, which it does, but also leaves the cells blank after I've
added firstname and lastname.

=IF(ISERROR((INDEX(Clients!$C$3:$C$1000,MATCH($K1& $L1,Clients!$A$3:$A$1000&Clients!$B$3:$B$1000,0))) ),"",(INDEX(Clients!$C$3:$C$1000,MATCH($K1&$L1,Cli ents!$A$3:$A$1000&Clients!$B$3:$B$1000,0))))

What am I doing wrong?

Office 2010
Win XP