First blank in a non contiguous range

You can try code like this. It selects the first blank cell in the range you specified, and you can change the range in the third line of the code.

Sub FindBlank()

    Dim rng As Range
    Set rng = Range("$F$15:$F$20,$F$22:$F$27,$F$29:$F$34,$F$36:$F$41")
    For Each cell In rng
        If cell.Value = "" Then cell.Select: Exit Sub
    Next cell
    
End Sub

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No need to iterate. You can use

Sub a()
Debug.Print Range("$F$15:$F$20,$F$22:$F$27,$F$29:$F$34,$F$36:$F$41").SpecialCells(xlCellTypeBlanks).Offset(, 1).Cells(1).Address
End Sub

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