If your text date field is formatted as you noted (dd-Mon-yy) I have a procedure that will convert that text field into a date field with the output pattern set to a US format (mm-dd-yyyy).
So that the current text field…
becomes a date field with this output…
Here is a procedure that simply adds a new field temporarily named tempDate and set to “date” type with the output pattern also set to US (or any other format you wish). This field is then filled with the date value taken from the existing text Date field (I’m assuming this field is currently named Date). We then delete the original Date field containing the text dates and change the new tempDate field’s name to Date. The noshow and endnoshow statements avoid screen redraws and vastly speed things up. The showother statement allows the newly created date type field to be properly displayed in the datasheet.
Test this on noncritical data since my personal testing is rather limited.