Distinct Count Measure on Varchar field

I need to create a Distinct count measure on a varchar field that exists in my fact table. the field is actually a Degenerate Dimension called Claim_Num.

When i try to create the distinct count measure on this field, it gives me the following error:

"SSAS distinct count measures requires numeric data type"

Is there a workaround for this? Possibly using MDX calculation?

thanks
Scott