Excel 2007中的VBA不会执行嵌套循环

Question

I've written nested For loops and even though the conditions are met it is not executing the code of the For loops. I tried commenting out the outermost For loop but the inner loop doesn't work either. I'm working in Excel 2007

Sub CalcAll()

Dim a As Integer
a = 10
Dim b As Integer
b = 10

For a = 10 To a = (Range("B" & Rows.Count).End(xlUp).Row) Step 1

    For b = 10 To b = (Worksheets("DistanceLookupTable").Cells(2, Sheet1.Columns.Count).End(xlToLeft).Column) Step 1

        If IsEmpty(Cells(a, i).Value) Then
            Exit Sub
        Else
            'Lots of code reading values from the worksheet and printing
            'calculated values to the worksheet 
        End If
    Next b 
Next a 
End Sub 

Thanks for your help

Answer 1

Your For loops should be written as:

For a = 10 To XXX

Rather than:

For a = 10 To a = XXX

Answer 2

Try this:

Dim a As Integer
'a = 10 'Unnecessary to assign value here, as you assign the starting value in the For loop
Dim b As Integer
'b = 10 'Again, this line not necessary

For a = 10 To Range("B" & Rows.Count).End(xlUp).Row Step 1

   For b = 10 To Worksheets("DistanceLookupTable").Cells(2, Sheet1.Columns.Count).End(xlToLeft).Column Step 1

      If IsEmpty(Cells(a, i).Value) Then '<- do you mean 'b' instead of 'i'? I don't see 'i' assigned anywhere...
         Exit Sub
      Else
        'Lots of code reading values from the worksheet and printing
        'calculated values to the worksheet 
      End If
   Next b 
Next a 

And on an unrelated note, you might consider fully qualifying your range in the first for loop ( Worksheets("worksheetName").Range("B" & Rows.Count)... instead of just Range("B" & Rows.Count)... ) As it is now, it will use the range of the currently active sheet. So unless that is your intention, it's better to be explicit.