Excel 2007 : IF...CONTAINS...THEN-link from another sheet

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SOLVED

Hi everybody.
I am trying to use an IF...CONTAINS...THEN formula.
So far this formula can search for "A" in cell G7 in the same sheet and return "1" or nothing: =IF(ISNUMBER(SEARCH("A",G7)),"1","")

I want to be able to change the G7 cell for a cell in another sheet or workbook. I wrote this formula to return a result from cell C20 in the SUMMARY TABLES worksheet, but its wrong:
=IF(ISNUMBER(SEARCH("A",'SUMMARY TABLES'!$C$20))"1","")

What corrections should I do to make it work?

Thank you!!