Fairly simply.. You can write a VBA function that you can actually embed in your SQL queries to do this. I went to Database Tools (Top of MS Access), Visual Basic, Right Click on the Modules Folder, Insert -> Module. After you write/copy the code, go to Debug at the top of the Visual Basic for Applications IDE and click "Compile YourDatabaseName.
See below:
Option Compare Database
Option Explicit
Public Function TrimString(fieldToTest As Variant) As Variant
Dim test, test2 As Variant
Dim trm As Variant
Dim intSearch, lngth As Integer
TrimString = Null
test = InStr(fieldToTest, "=")
test2 = InStr(fieldToTest, ":")
lngth = Len(fieldToTest)
If test > 0 Then
    'We know it contains an equals sign
    trm = Left(fieldToTest, test - 1)
    trm = Trim(trm)
    Debug.Print trm
ElseIf test2 > 0 Then
    'We know it contains a colon
    trm = Left(fieldToTest, test2 - 1)
    trm = Trim(trm)
    Debug.Print trm
ElseIf lngth > 0 Then
    'Find out if it has integers in it
    'Rebuild the string without Integers
    For intSearch = 1 To lngth
         If Not IsNumeric(Mid$(fieldToTest, intSearch, 1)) Then
          trm = trm & Mid$(fieldToTest, intSearch, 1)
        Else
        End If
    Next
    trm = Trim(trm)
Else
    'Regular String
    'Do Nothing
    trm = fieldToTest
End If
TrimString = trm
End Function
There's not very much error handling, but I think this answers your question.
I threw it in a Table, field data type is Text: 
Table
ID  stringTest (Field Name)
 1. randomtext = 123453
 2. otherrandmtext = 543555
 3. evendifferentone : 453553
 4. andsoon : 05453534
Output :
 ID Expr1
 1. randomtext
 2. otherrandmtext
 3. evendifferentone
 4. andsoon
SQL :
SELECT Table2.ID, 
TrimString([stringTest]) AS Expr1
FROM Table2;
Recall from the VBA code that TrimString is the function name.
If there is anything I overlooked - please let me know and I will do my best to correct it.