Consider you have 101 frequency monitors and you have named those monitors 'Freq=0.5e9', 'Freq=2e9' etc. Then you can use macro to select the results for each monitor in the loop and export the data. See sample below:
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Sub Main ()
For ii=0.5e9 To 2e9 STEP 0.015e9
SelectTreeItem ("2D/3D Results\E-Field\e-field Freq="&ii&"")
With ASCIIExport
.Reset
.FileName (".\E_FIELD_FREQ_"&ii&".dat")
.StepX (0.1)
.StepY (0.1)
.StepZ (0.1)
.Mode ("FixedWidth")
.Execute
End With
SelectTreeItem ("2D/3D Results\H-Field\h-field Freq="&ii&"")
With ASCIIExport
.Reset
.FileName (".\H_FIELD_FREQ_"&ii&".dat")
.StepX (0.1)
.StepY (0.1)
.StepZ (0.1)
.Mode ("FixedWidth")
.Execute
End With
Next
End Sub
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You might need to adjust the macro to the naming style you use for your field monitors.