MaxVal Function

Hello,

I need to output the hole depth on a boring log by finding the deepest value from several tables/fields.  This is the expression I used, but it isn't working.   I've checked all the table/field names and report variables, and it seems like it should work ... Does anyone have a suggestion?

BOTTOM OF EXPLORATION _
<<Format(<<MaxVal(<<POINT.HoleDepth>>,<<Report Var.SAMPLE Bottom>>,<<Report Var.DYE TEST RESULTS Bottom>>,<<CORE DATA.Bottom>>,<<STRATIGRAPHY.Bottom>>)>>, 0.0_
)>> FT

The Report Variables are:

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