Too many arguments for this function error

Excel 2007 keeps tellign me I entered too many arguments for this formula:

=IF(ISNUMBER(SEARCH("F",IF(ISNUMBER(SEARCH("SP",mergedText('CV-22 Wkly Checkerboard'!$C$7))),if('Wkly Fly Sched'!$C$4="SP", “SP”, mergedText('CV-22 Wkly Checkerboard'!$C$7), mergedText('CV-22 Wkly Checkerboard'!$C$7))),'Wkly Fly Sched'!$C$4,mergedText('CV-22 Wkly Checkerboard'!$C$7))

The purpose is to check the checkerboard sheet for one of either two text values, "f" or "SP". If the cell text value starts with an "F" it then reads the values from the wkly fly sched sheet, if flase it uses the values in the checkerboard. If it is a "SP" then it cross checks the fly sched sheet to verify that it contains the text "SP" if so it defualts to "SP" else it reads the values from the checkerboard.

The mergedText is a user defined function to read the values of merged cells in the checkerboard sheet. I have no control over the way the checkerboard is built, we simply paste that data in from the original workbook, which is why I had to use a mergedtext function.

---------- Post added at 08:45 AM ---------- Previous post was at 08:33 AM ----------

Problem solved. I also had my flaw in my logic flow for the desired outcome.

=IF(ISNUMBER(SEARCH("F",mergedText('CV-22 Wkly Checkerboard'!C7))),IF('Wkly Fly Sched'!C4="", " ", 'Wkly Fly Sched'!C4),IF(AND(mergedText('CV-22 Wkly Checkerboard'!C7)="SP",'Wkly Fly Sched'!C4<>""),IF('Wkly Fly Sched'!C4="", " ", 'Wkly Fly Sched'!C4),IF(AND('Wkly Fly Sched'!C4=""),mergedText('CV-22 Wkly Checkerboard'!C7),mergedText('CV-22 Wkly Checkerboard'!C7))))