# Specifying an External Reference in a Formula

Learn how to use external references in formulas and access data from an xlsx file in this comprehensive guide.

## Content

You can use external references in formulas, such as data from an xlsx file.
The external reference uses the file name and sheet. For example: 'C:\\\Mescius\\\[Sum.xlsx]Sheet1'!.

## Using Code

The following example references data from a file.

```csharp
fpSpread1.Sheets[0].SetFormula(0, 0, "SUM('C:\\Program Files (x86)\\Mescius\\[Sum.xlsx]Sheet1'!A1:A4)");
                fpSpread1.AllowUserFormulas = true;
```

```vbnet
FpSpread1.Sheets(0).SetFormula(0, 0, "SUM('C:\Program Files (x86)\Mescius\[Sum.xlsx]Sheet1'!A1:A4)")
                FpSpread1.AllowUserFormulas = True
```

## See Also

[Formulas in Cells](/spreadnet/docs/latest/online-win/overview/spwin-devguide/spwin-cell-formula)
[Placing a Formula in Cells](/spreadnet/docs/latest/online-win/overview/spwin-devguide/spwin-cell-formula/spwin-formulaplace)
[Specifying a Cell Reference in a Formula](/spreadnet/docs/latest/online-win/overview/spwin-devguide/spwin-cell-formula/spwin-formulacellref)
[Specifying a Sheet Reference in a Formula](/spreadnet/docs/latest/online-win/overview/spwin-devguide/spwin-cell-formula/spwin-formulasheetref)
[Using a Circular Reference in a Formula](/spreadnet/docs/latest/online-win/overview/spwin-devguide/spwin-cell-formula/spwin-formulacircref)
[Nesting Functions in a Formula](/spreadnet/docs/latest/online-win/overview/spwin-devguide/spwin-cell-formula/spwin-formulanested)
[Recalculating and Updating Formulas Automatically](/spreadnet/docs/latest/online-win/overview/spwin-devguide/spwin-cell-formula/spwin-formularecalc)
[Finding a Value Using GoalSeek](/spreadnet/docs/latest/online-win/overview/spwin-devguide/spwin-cell-formula/spwin-formula-goalseek)
[Allowing the User to Enter Formulas](/spreadnet/docs/latest/online-win/overview/spwin-devguide/spwin-cell-formula/spwin-formulaallowuser)
[Creating and Using a Custom Name](/spreadnet/docs/latest/online-win/overview/spwin-devguide/spwin-cell-formula/spwin-formulacustomname)
[Creating and Using a Custom Function](/spreadnet/docs/latest/online-win/overview/spwin-devguide/spwin-cell-formula/spwin-formulacustomfunc)
[Creating and Using External Variable](/spreadnet/docs/latest/online-win/overview/spwin-devguide/spwin-cell-formula/spwin-external-variable)
[Using the Array Formula](/spreadnet/docs/latest/online-win/overview/spwin-devguide/spwin-cell-formula/spwin-arrayformula)
[Working with the Formula Text Box](/spreadnet/docs/latest/online-win/overview/spwin-devguide/spwin-cell-formula/spwin-formulabar)
[Setting up the Name Box](/spreadnet/docs/latest/online-win/overview/spwin-devguide/spwin-cell-formula/spwin-namebox)
[Using Language Package](/spreadnet/docs/latest/online-win/overview/spwin-devguide/spwin-cell-formula/UsingLanguagePackage)
[Accessing Data from Header or Footer](/spreadnet/docs/latest/online-win/overview/spwin-devguide/spwin-cell-formula/spwin-headerfooterformula)
[Managing External Reference](/spreadnet/docs/latest/online-win/overview/spwin-devguide/spwin-cell-formula/spwin-extrenalreference)
[Working With Dynamic Array Formulas](/spreadnet/docs/latest/online-win/overview/spwin-devguide/spwin-cell-formula/WorkingWithDynamicArrayFormulas)