Converting numeric to non-numeric?

I'm a beginner to Crystal. Honestly, I had no intention of learning it beyond a user level but our developer is MIA and we need to tweak our template. We have a field that use to be a number (a "MapID" in this case), it would be 1, 2, 3, 4, etc. Now we want it to reflect a different ID that is going to look like 1a, 1b, 1c, 2, 3a, etc. I've changed the RPT query in access to populate with the new ID, keeping the column the same, but of course nothing in life is that simple. When trying to export the Crystal Template to PDF I get this error almost immediately:

"The string is non-numeric"

The Formula Workshop pops up and says this:

CDbl({RPT_Detailed_Findings.MAPID})

By going to the subreport and right clicking on the specific field and going to Edit Formula the Formula Workshop says this:

If {?Pm-RPT_Detailed_Findings.source} = "mapped" then
{?Pm-RPT_Executive_Summary.MAPID}
else "Unmapped";

I am so new to this I can't really see why it would only accept a number, my only guess is that the restriction has to do with "CDbl" or "?PM". Am I even close?

I'm in a jam here as there is nobody else to go to in the company, I'm it. And the developer is non-responsive.

Thanks for the help.remove cDbl,

as 1a ur new id is already string, u cannot convert it to a double numeric value

Hope it helps|||Now they are all out of order and the letters still did not come in, also I believe only the records that did not have letters made it into the report. The report exported though.