More likely the "formula" you are entering in the cell is invalid. It must look the same as if you entered it by hand on the worksheet. Always view these in the immediate window or in a msgbox when testing.
Note: I see no reason for an array formula here. Also, why the ;@ at the end of the format string (hh:mm:ss;@) - I'm not sure what that does - can you educate me?Code:Dim sFormula As String sFormula = "=IF(MOD(A1,1) >= TIMEVALUE(" & Chr(34) & timeCompare & Chr(34) & "),1,0)" debug.print sFormula Range("A3").Formula = sFormula