diff --git a/crates/engine/src/cmd/data.rs b/crates/engine/src/cmd/data.rs
index 32ec866..cb793e7 100644
--- a/crates/engine/src/cmd/data.rs
+++ b/crates/engine/src/cmd/data.rs
@@ -952,10 +952,26 @@ pub fn check_validation(wb: &Workbook, sheet: usize, at: CellRef, input: &str) -
         return None;
     }
     let v = gridcraft_core::parse::parse_input(input, wb.date_system).value;
-    let num = |f: &str| gridcraft_calc::evaluate(wb, sheet, at, f).to_number().ok();
+    // The formulas are written for the first cell of the range and see the value being entered,
+    // as in Excel (a custom `=A1>10` on A1:A9 checks A5's new value at A5).
+    let first = dv.ranges.first().map(|r| r.start).unwrap_or(at);
+    let entered;
+    let wb = if sh.value(at) == v {
+        wb
+    } else {
+        let mut w = wb.clone();
+        if let Some(sh) = w.sheet_mut(sheet) {
+            let style = sh.style_id(at);
+            sh.cells.set(at, Cell { value: v.clone(), style, ..Default::default() });
+        }
+        entered = w;
+        &entered
+    };
+    let eval = |f: &str| gridcraft_calc::evaluate(wb, sheet, at, &formula_at(f, first, at));
+    let num = |f: &str| eval(f).to_number().ok();
     let ok = match dv.kind {
         ValidationKind::List => list_items(wb, sheet, dv).iter().any(|x| x.eq_ignore_ascii_case(input)),
-        ValidationKind::Custom => gridcraft_calc::evaluate(wb, sheet, at, &dv.f1).to_bool().unwrap_or(false),
+        ValidationKind::Custom => eval(&dv.f1).to_bool().unwrap_or(false),
         ValidationKind::TextLength => {
             let n = input.chars().count() as f64;
             compare_op(dv.op, n, num(&dv.f1), dv.f2.as_deref().and_then(num))
@@ -982,6 +998,21 @@ pub fn check_validation(wb: &Workbook, sheet: usize, at: CellRef, input: &str) -
     Some((dv.clone(), msg))
 }
 
+/// A formula written for `first`, as seen from `at` (relative references shifted).
+fn formula_at(f: &str, first: CellRef, at: CellRef) -> String {
+    if first == at {
+        return f.to_string();
+    }
+    match gridcraft_formula::parse(f.trim_start_matches('=')) {
+        Ok(e) => gridcraft_formula::print(&gridcraft_formula::adjust::shift_relative(
+            e,
+            at.row as i64 - first.row as i64,
+            at.col as i64 - first.col as i64,
+        )),
+        Err(_) => f.to_string(),
+    }
+}
+
 fn compare_op(op: CfOperator, n: f64, a: Option<f64>, b: Option<f64>) -> bool {
     let Some(a) = a else { return false };
     match op {
diff --git a/crates/engine/src/tests.rs b/crates/engine/src/tests.rs
index cddff22..4fb9df4 100644
--- a/crates/engine/src/tests.rs
+++ b/crates/engine/src/tests.rs
@@ -1257,6 +1257,19 @@ fn ods_import_never_reuses_source_as_save_target() {
     std::fs::remove_dir_all(dir).unwrap();
 }
 
+#[test]
+fn validation_formulas_are_relative_and_see_the_new_value() {
+    let mut s = s();
+    s.execute("range.setValues", json!({"range": "B1", "values": [[1], [100]]})).unwrap();
+    s.execute("data.validation", json!({"range": "A1:A2", "type": "custom", "formula1": "=A1>10"})).unwrap();
+    s.execute("data.validation", json!({"range": "C1:C2", "type": "whole", "operator": "lessOrEqual", "formula1": "=B1"})).unwrap();
+    let ok = |s: &mut Session, cell: &str, input: &str| s.execute("data.validate", json!({"cell": cell, "input": input})).unwrap()["ok"] == true;
+    assert!(ok(&mut s, "A1", "20"));
+    assert!(!ok(&mut s, "A2", "5"));
+    assert!(ok(&mut s, "C2", "50"));
+    assert!(!ok(&mut s, "C1", "50"));
+}
+
 #[test]
 fn samples_build() {
     for (name, _) in crate::sample::SAMPLES {