Code:
I will make sure the data type is number
If this "PMT000243" is what you're referring to, you cannot. Number field types cannot contain alpha or most other special characters. June's example was for text (sometimes aka alphanumeric) and will work with text values. The difference is mainly in the way the parts of the expression are delimited for text
If you're using alpha prefixes to distinguish between Payment and Receipts, (for example REC000123 is for receipts) you might be better off separating the alpha from the numeric and stringing them together in a form control.
Right now, I don't know where this is at or where it's going.