diff --git a/src/gui_qt/io/asciireader.py b/src/gui_qt/io/asciireader.py
index 8cbbd37..a4c9524 100644
--- a/src/gui_qt/io/asciireader.py
+++ b/src/gui_qt/io/asciireader.py
@@ -3,7 +3,7 @@ from __future__ import annotations
 import re
 
 from nmreval.io.asciireader import AsciiReader
-from nmreval.utils import NUMBER_RE
+from nmreval.utils import NUMBER_RE, numbers_from_string
 
 from ..Qt import QtGui, QtCore, QtWidgets
 from .._py.asciidialog import Ui_ascii_reader
@@ -243,19 +243,31 @@ class QAsciiReader(QtWidgets.QDialog, Ui_ascii_reader):
         if self.reader is None:
             return
 
-        try:
-            pattern = re.compile(pattern)
-            self.regex_input.setStyleSheet('color: rgb(0, 0, 0)')
-            self._matches = [m for m in pattern.finditer(str(self.reader.fname.stem))]
-        except re.error:
-            self._matches = []
+        success = True
+        self._matches = []
 
-        if self._matches:
+        if pattern:
+            try:
+                re_pattern = re.compile(pattern)
+            except re.error:
+                success = False
+            else:
+                self._matches = [m for m in re_pattern.finditer(str(self.reader.fname.stem))]
+        else:
+            success = False
+
+        # matches exist and have numbers in them
+        if self._matches and all([len(numbers_from_string(m.group())) for m in self._matches]):
             self.re_match_index.blockSignals(True)
             self.re_match_index.setMaximum(len(self._matches))
             self.re_match_index.blockSignals(False)
         else:
-            self.regex_input.setStyleSheet('color: rgb(255, 0, 0)')
+            success = False
+
+        if success:
+            self.regex_input.setStyleSheet('color: rgb(0, 0, 0)')
+        else:
+            self.regex_input.setStyleSheet('background-color: rgba(255, 0, 0, 50)')
 
         self.show_match(self.re_match_index.value())
 
@@ -273,7 +285,9 @@ class QAsciiReader(QtWidgets.QDialog, Ui_ascii_reader):
         val = 0
         if self.re_button.isChecked() and self._matches:
             m = self._matches[self.re_match_index.value()-1]
-            val = float(NUMBER_RE.search(m.group()).group().replace('p', '.'))
+            val = numbers_from_string(m.group())
+            # numbers_from returns list of floats we use first match if available
+            val = val[0] if val else 0.0
         elif self.custom_button.isChecked():
             val = float(self.custom_input.text())
 
diff --git a/src/nmreval/utils/__init__.py b/src/nmreval/utils/__init__.py
index 24e8009..64ec28c 100755
--- a/src/nmreval/utils/__init__.py
+++ b/src/nmreval/utils/__init__.py
@@ -5,3 +5,11 @@ from .constants import *
 
 NUMBER_RE = re.compile(r'[-+]?\d*[+p.]?\d+([eE][-+]?\d+)?', re.MULTILINE)
 UNSIGNED_NUMBER_RE = re.compile(r'[-+]?\d*[+p.]?\d+([eE][-+]?\d+)?', re.MULTILINE)
+
+
+def numbers_from_string(any_string: str) -> list[float]:
+    print(any_string)
+    matches = []
+    for m in NUMBER_RE.finditer(any_string):
+        matches.append(float(m.group().replace('p', '.')))
+    return matches